diff --git a/ethcore/src/account.rs b/ethcore/src/account.rs
index 29922dda5..d0628436d 100644
--- a/ethcore/src/account.rs
+++ b/ethcore/src/account.rs
@@ -166,16 +166,16 @@ impl Account {
 		!self.code_cache.is_empty() || (self.code_cache.is_empty() && self.code_hash == Some(SHA3_EMPTY))
 	}
 
-	/// Provide a database to lookup `code_hash`. Should not be called if it is a contract without code.
+	/// Provide a database to get `code_hash`. Should not be called if it is a contract without code.
 	pub fn cache_code(&mut self, db: &AccountDB) -> bool {
 		// TODO: fill out self.code_cache;
 		trace!("Account::cache_code: ic={}; self.code_hash={:?}, self.code_cache={}", self.is_cached(), self.code_hash, self.code_cache.pretty());
 		self.is_cached() ||
 			match self.code_hash {
-				Some(ref h) => match db.lookup(h) {
+				Some(ref h) => match db.get(h) {
 					Some(x) => { self.code_cache = x.to_vec(); true },
 					_ => {
-						warn!("Failed reverse lookup of {}", h);
+						warn!("Failed reverse get of {}", h);
 						false
 					},
 				},
diff --git a/ethcore/src/account_db.rs b/ethcore/src/account_db.rs
index c21ea2993..7337940da 100644
--- a/ethcore/src/account_db.rs
+++ b/ethcore/src/account_db.rs
@@ -30,18 +30,18 @@ impl<'db> HashDB for AccountDB<'db>{
 		unimplemented!()
 	}
 
-	fn lookup(&self, key: &H256) -> Option<&[u8]> {
+	fn get(&self, key: &H256) -> Option<&[u8]> {
 		if key == &SHA3_NULL_RLP {
 			return Some(&NULL_RLP_STATIC);
 		}
-		self.db.lookup(&combine_key(&self.address, key))
+		self.db.get(&combine_key(&self.address, key))
 	}
 
-	fn exists(&self, key: &H256) -> bool {
+	fn contains(&self, key: &H256) -> bool {
 		if key == &SHA3_NULL_RLP {
 			return true;
 		}
-		self.db.exists(&combine_key(&self.address, key))
+		self.db.contains(&combine_key(&self.address, key))
 	}
 
 	fn insert(&mut self, _value: &[u8]) -> H256 {
@@ -52,7 +52,7 @@ impl<'db> HashDB for AccountDB<'db>{
 		unimplemented!()
 	}
 
-	fn kill(&mut self, _key: &H256) {
+	fn remove(&mut self, _key: &H256) {
 		unimplemented!()
 	}
 }
@@ -82,18 +82,18 @@ impl<'db> HashDB for AccountDBMut<'db>{
 		unimplemented!()
 	}
 
-	fn lookup(&self, key: &H256) -> Option<&[u8]> {
+	fn get(&self, key: &H256) -> Option<&[u8]> {
 		if key == &SHA3_NULL_RLP {
 			return Some(&NULL_RLP_STATIC);
 		}
-		self.db.lookup(&combine_key(&self.address, key))
+		self.db.get(&combine_key(&self.address, key))
 	}
 
-	fn exists(&self, key: &H256) -> bool {
+	fn contains(&self, key: &H256) -> bool {
 		if key == &SHA3_NULL_RLP {
 			return true;
 		}
-		self.db.exists(&combine_key(&self.address, key))
+		self.db.contains(&combine_key(&self.address, key))
 	}
 
 	fn insert(&mut self, value: &[u8]) -> H256 {
@@ -114,12 +114,12 @@ impl<'db> HashDB for AccountDBMut<'db>{
 		self.db.emplace(key, value.to_vec())
 	}
 
-	fn kill(&mut self, key: &H256) {
+	fn remove(&mut self, key: &H256) {
 		if key == &SHA3_NULL_RLP {
 			return;
 		}
 		let key = combine_key(&self.address, key);
-		self.db.kill(&key)
+		self.db.remove(&key)
 	}
 }
 
diff --git a/util/src/hashdb.rs b/util/src/hashdb.rs
index 0a5f13d52..1ec3069d8 100644
--- a/util/src/hashdb.rs
+++ b/util/src/hashdb.rs
@@ -20,12 +20,10 @@ use bytes::*;
 use std::collections::HashMap;
 
 /// Trait modelling datastore keyed by a 32-byte Keccak hash.
-pub trait HashDB : AsHashDB {
+pub trait HashDB: AsHashDB {
 	/// Get the keys in the database together with number of underlying references.
 	fn keys(&self) -> HashMap<H256, i32>;
 
-	/// Deprecated. use `get`.
-	fn lookup(&self, key: &H256) -> Option<&[u8]>; // TODO: rename to get.
 	/// Look up a given hash into the bytes that hash to it, returning None if the
 	/// hash is not known.
 	///
@@ -41,10 +39,8 @@ pub trait HashDB : AsHashDB {
 	///   assert_eq!(m.get(&hash).unwrap(), hello_bytes);
 	/// }
 	/// ```
-	fn get(&self, key: &H256) -> Option<&[u8]> { self.lookup(key) }
+	fn get(&self, key: &H256) -> Option<&[u8]>;
 
-	/// Deprecated. Use `contains`.
-	fn exists(&self, key: &H256) -> bool; // TODO: rename to contains.
 	/// Check for the existance of a hash-key.
 	///
 	/// # Examples
@@ -63,10 +59,10 @@ pub trait HashDB : AsHashDB {
 	///   assert!(!m.contains(&key));
 	/// }
 	/// ```
-	fn contains(&self, key: &H256) -> bool { self.exists(key) }
+	fn contains(&self, key: &H256) -> bool;
 
 	/// Insert a datum item into the DB and return the datum's hash for a later lookup. Insertions
-	/// are counted and the equivalent number of `kill()`s must be performed before the data
+	/// are counted and the equivalent number of `remove()`s must be performed before the data
 	/// is considered dead.
 	///
 	/// # Examples
@@ -86,8 +82,6 @@ pub trait HashDB : AsHashDB {
 	/// Like `insert()` , except you provide the key and the data is all moved.
 	fn emplace(&mut self, key: H256, value: Bytes);
 
-	/// Deprecated - use `remove`.
-	fn kill(&mut self, key: &H256); // TODO: rename to remove.
 	/// Remove a datum previously inserted. Insertions can be "owed" such that the same number of `insert()`s may
 	/// happen without the data being eventually being inserted into the DB.
 	///
@@ -109,7 +103,7 @@ pub trait HashDB : AsHashDB {
 	///   assert_eq!(m.get(key).unwrap(), d);
 	/// }
 	/// ```
-	fn remove(&mut self, key: &H256) { self.kill(key) }
+	fn remove(&mut self, key: &H256);
 }
 
 /// Upcast trait.
@@ -121,6 +115,10 @@ pub trait AsHashDB {
 }
 
 impl<T: HashDB> AsHashDB for T {
-	fn as_hashdb(&self) -> &HashDB { self }
-	fn as_hashdb_mut(&mut self) -> &mut HashDB { self }
+	fn as_hashdb(&self) -> &HashDB {
+		self
+	}
+	fn as_hashdb_mut(&mut self) -> &mut HashDB {
+		self
+	}
 }
diff --git a/util/src/journaldb/archivedb.rs b/util/src/journaldb/archivedb.rs
index 0381c08ea..c7f6b92fa 100644
--- a/util/src/journaldb/archivedb.rs
+++ b/util/src/journaldb/archivedb.rs
@@ -98,7 +98,7 @@ impl HashDB for ArchiveDB {
 		ret
 	}
 
-	fn lookup(&self, key: &H256) -> Option<&[u8]> {
+	fn get(&self, key: &H256) -> Option<&[u8]> {
 		let k = self.overlay.raw(key);
 		match k {
 			Some(&(ref d, rc)) if rc > 0 => Some(d),
@@ -113,8 +113,8 @@ impl HashDB for ArchiveDB {
 		}
 	}
 
-	fn exists(&self, key: &H256) -> bool {
-		self.lookup(key).is_some()
+	fn contains(&self, key: &H256) -> bool {
+		self.get(key).is_some()
 	}
 
 	fn insert(&mut self, value: &[u8]) -> H256 {
@@ -123,8 +123,8 @@ impl HashDB for ArchiveDB {
 	fn emplace(&mut self, key: H256, value: Bytes) {
 		self.overlay.emplace(key, value);
 	}
-	fn kill(&mut self, key: &H256) {
-		self.overlay.kill(key);
+	fn remove(&mut self, key: &H256) {
+		self.overlay.remove(key);
 	}
 }
 
@@ -207,7 +207,7 @@ mod tests {
 		jdb.commit(5, &b"1004a".sha3(), Some((3, b"1002a".sha3()))).unwrap();
 		jdb.commit(6, &b"1005a".sha3(), Some((4, b"1003a".sha3()))).unwrap();
 
-		assert!(jdb.exists(&x));
+		assert!(jdb.contains(&x));
 	}
 
 	#[test]
@@ -216,14 +216,14 @@ mod tests {
 		let mut jdb = ArchiveDB::new_temp();
 		let h = jdb.insert(b"foo");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.remove(&h);
 		jdb.commit(1, &b"1".sha3(), None).unwrap();
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(2, &b"2".sha3(), None).unwrap();
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(3, &b"3".sha3(), Some((0, b"0".sha3()))).unwrap();
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(4, &b"4".sha3(), Some((1, b"1".sha3()))).unwrap();
 	}
 
@@ -235,26 +235,26 @@ mod tests {
 		let foo = jdb.insert(b"foo");
 		let bar = jdb.insert(b"bar");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 
 		jdb.remove(&foo);
 		jdb.remove(&bar);
 		let baz = jdb.insert(b"baz");
 		jdb.commit(1, &b"1".sha3(), Some((0, b"0".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		let foo = jdb.insert(b"foo");
 		jdb.remove(&baz);
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&baz));
 
 		jdb.remove(&foo);
 		jdb.commit(3, &b"3".sha3(), Some((2, b"2".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.commit(4, &b"4".sha3(), Some((3, b"3".sha3()))).unwrap();
 	}
@@ -267,8 +267,8 @@ mod tests {
 		let foo = jdb.insert(b"foo");
 		let bar = jdb.insert(b"bar");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 
 		jdb.remove(&foo);
 		let baz = jdb.insert(b"baz");
@@ -277,12 +277,12 @@ mod tests {
 		jdb.remove(&bar);
 		jdb.commit(1, &b"1b".sha3(), Some((0, b"0".sha3()))).unwrap();
 
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -292,16 +292,16 @@ mod tests {
 
 		let foo = jdb.insert(b"foo");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.remove(&foo);
 		jdb.commit(1, &b"1".sha3(), Some((0, b"0".sha3()))).unwrap();
 		jdb.insert(b"foo");
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 		jdb.commit(3, &b"2".sha3(), Some((0, b"2".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -315,10 +315,10 @@ mod tests {
 
 		jdb.insert(b"foo");
 		jdb.commit(1, &b"1b".sha3(), Some((0, b"0".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.commit(2, &b"2a".sha3(), Some((1, b"1a".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -344,8 +344,8 @@ mod tests {
 
 		{
 			let mut jdb = ArchiveDB::new(dir.to_str().unwrap(), None);
-			assert!(jdb.exists(&foo));
-			assert!(jdb.exists(&bar));
+			assert!(jdb.contains(&foo));
+			assert!(jdb.contains(&bar));
 			jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 		}
 	}
@@ -373,7 +373,7 @@ mod tests {
 			let mut jdb = ArchiveDB::new(dir.to_str().unwrap(), None);
 			jdb.remove(&foo);
 			jdb.commit(3, &b"3".sha3(), Some((2, b"2".sha3()))).unwrap();
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 			jdb.remove(&foo);
 			jdb.commit(4, &b"4".sha3(), Some((3, b"3".sha3()))).unwrap();
 			jdb.commit(5, &b"5".sha3(), Some((4, b"4".sha3()))).unwrap();
@@ -402,7 +402,7 @@ mod tests {
 		{
 			let mut jdb = ArchiveDB::new(dir.to_str().unwrap(), None);
 			jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 		}
 	}
 
diff --git a/util/src/journaldb/earlymergedb.rs b/util/src/journaldb/earlymergedb.rs
index e495b9d03..71959fa35 100644
--- a/util/src/journaldb/earlymergedb.rs
+++ b/util/src/journaldb/earlymergedb.rs
@@ -172,8 +172,8 @@ impl EarlyMergeDB {
 		trace!(target: "jdb.fine", "replay_keys: (end) refs={:?}", refs);
 	}
 
-	fn kill_keys(deletes: &[H256], refs: &mut HashMap<H256, RefInfo>, batch: &DBTransaction, from: RemoveFrom, trace: bool) {
-		// with a kill on {queue_refs: 1, in_archive: true}, we have two options:
+	fn remove_keys(deletes: &[H256], refs: &mut HashMap<H256, RefInfo>, batch: &DBTransaction, from: RemoveFrom, trace: bool) {
+		// with a remove on {queue_refs: 1, in_archive: true}, we have two options:
 		// - convert to {queue_refs: 1, in_archive: false} (i.e. remove it from the conceptual archive)
 		// - convert to {queue_refs: 0, in_archive: true} (i.e. remove it from the conceptual queue)
 		// (the latter option would then mean removing the RefInfo, since it would no longer be counted in the queue.)
@@ -186,13 +186,13 @@ impl EarlyMergeDB {
 					c.in_archive = false;
 					Self::reset_already_in(batch, h);
 					if trace {
-						trace!(target: "jdb.fine", "    kill({}): In archive, 1 in queue: Reducing to queue only and recording", h);
+						trace!(target: "jdb.fine", "    remove({}): In archive, 1 in queue: Reducing to queue only and recording", h);
 					}
 					continue;
 				} else if c.queue_refs > 1 {
 					c.queue_refs -= 1;
 					if trace {
-						trace!(target: "jdb.fine", "    kill({}): In queue > 1 refs: Decrementing ref count to {}", h, c.queue_refs);
+						trace!(target: "jdb.fine", "    remove({}): In queue > 1 refs: Decrementing ref count to {}", h, c.queue_refs);
 					}
 					continue;
 				} else {
@@ -204,14 +204,14 @@ impl EarlyMergeDB {
 					refs.remove(h);
 					Self::reset_already_in(batch, h);
 					if trace {
-						trace!(target: "jdb.fine", "    kill({}): In archive, 1 in queue: Removing from queue and leaving in archive", h);
+						trace!(target: "jdb.fine", "    remove({}): In archive, 1 in queue: Removing from queue and leaving in archive", h);
 					}
 				}
 				Some(RefInfo{queue_refs: 1, in_archive: false}) => {
 					refs.remove(h);
 					batch.delete(&h.bytes()).expect("Low-level database error. Some issue with your hard disk?");
 					if trace {
-						trace!(target: "jdb.fine", "    kill({}): Not in archive, only 1 ref in queue: Removing from queue and DB", h);
+						trace!(target: "jdb.fine", "    remove({}): Not in archive, only 1 ref in queue: Removing from queue and DB", h);
 					}
 				}
 				None => {
@@ -219,7 +219,7 @@ impl EarlyMergeDB {
 					//assert!(!Self::is_already_in(db, &h));
 					batch.delete(&h.bytes()).expect("Low-level database error. Some issue with your hard disk?");
 					if trace {
-						trace!(target: "jdb.fine", "    kill({}): Not in queue - MUST BE IN ARCHIVE: Removing from DB", h);
+						trace!(target: "jdb.fine", "    remove({}): Not in queue - MUST BE IN ARCHIVE: Removing from DB", h);
 					}
 				}
 				_ => panic!("Invalid value in refs: {:?}", n),
@@ -290,7 +290,7 @@ impl HashDB for EarlyMergeDB {
 		ret
 	}
 
-	fn lookup(&self, key: &H256) -> Option<&[u8]> {
+	fn get(&self, key: &H256) -> Option<&[u8]> {
 		let k = self.overlay.raw(key);
 		match k {
 			Some(&(ref d, rc)) if rc > 0 => Some(d),
@@ -305,8 +305,8 @@ impl HashDB for EarlyMergeDB {
 		}
 	}
 
-	fn exists(&self, key: &H256) -> bool {
-		self.lookup(key).is_some()
+	fn contains(&self, key: &H256) -> bool {
+		self.get(key).is_some()
 	}
 
 	fn insert(&mut self, value: &[u8]) -> H256 {
@@ -315,8 +315,8 @@ impl HashDB for EarlyMergeDB {
 	fn emplace(&mut self, key: H256, value: Bytes) {
 		self.overlay.emplace(key, value);
 	}
-	fn kill(&mut self, key: &H256) {
-		self.overlay.kill(key);
+	fn remove(&mut self, key: &H256) {
+		self.overlay.remove(key);
 	}
 }
 
@@ -472,7 +472,7 @@ impl JournalDB for EarlyMergeDB {
 					if trace {
 						trace!(target: "jdb.ops", "  Expunging: {:?}", deletes);
 					}
-					Self::kill_keys(&deletes, &mut refs, &batch, RemoveFrom::Archive, trace);
+					Self::remove_keys(&deletes, &mut refs, &batch, RemoveFrom::Archive, trace);
 
 					if trace {
 						trace!(target: "jdb.ops", "  Finalising: {:?}", inserts);
@@ -504,7 +504,7 @@ impl JournalDB for EarlyMergeDB {
 					if trace {
 						trace!(target: "jdb.ops", "  Reverting: {:?}", inserts);
 					}
-					Self::kill_keys(&inserts, &mut refs, &batch, RemoveFrom::Queue, trace);
+					Self::remove_keys(&inserts, &mut refs, &batch, RemoveFrom::Queue, trace);
 				}
 
 				try!(batch.delete(&last));
@@ -565,7 +565,7 @@ mod tests {
 		jdb.commit(6, &b"1005a".sha3(), Some((4, b"1003a".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 
-		assert!(jdb.exists(&x));
+		assert!(jdb.contains(&x));
 	}
 
 	#[test]
@@ -584,8 +584,8 @@ mod tests {
 		assert!(jdb.can_reconstruct_refs());
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 	}
 
 	#[test]
@@ -595,20 +595,20 @@ mod tests {
 		let h = jdb.insert(b"foo");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.remove(&h);
 		jdb.commit(1, &b"1".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(2, &b"2".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(3, &b"3".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(4, &b"4".sha3(), Some((1, b"1".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(!jdb.exists(&h));
+		assert!(!jdb.contains(&h));
 	}
 
 	#[test]
@@ -620,38 +620,38 @@ mod tests {
 		let bar = jdb.insert(b"bar");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 
 		jdb.remove(&foo);
 		jdb.remove(&bar);
 		let baz = jdb.insert(b"baz");
 		jdb.commit(1, &b"1".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		let foo = jdb.insert(b"foo");
 		jdb.remove(&baz);
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		jdb.remove(&foo);
 		jdb.commit(3, &b"3".sha3(), Some((2, b"2".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(!jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(!jdb.contains(&baz));
 
 		jdb.commit(4, &b"4".sha3(), Some((3, b"3".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(!jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(!jdb.exists(&baz));
+		assert!(!jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(!jdb.contains(&baz));
 	}
 
 	#[test]
@@ -663,8 +663,8 @@ mod tests {
 		let bar = jdb.insert(b"bar");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 
 		jdb.remove(&foo);
 		let baz = jdb.insert(b"baz");
@@ -675,15 +675,15 @@ mod tests {
 		jdb.commit(1, &b"1b".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&baz));
-		assert!(!jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&baz));
+		assert!(!jdb.contains(&bar));
 	}
 
 	#[test]
@@ -694,19 +694,19 @@ mod tests {
 		let foo = jdb.insert(b"foo");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.remove(&foo);
 		jdb.commit(1, &b"1".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 		jdb.insert(b"foo");
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 		jdb.commit(3, &b"2".sha3(), Some((0, b"2".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -730,11 +730,11 @@ mod tests {
 		jdb.commit(1, &b"1c".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.commit(2, &b"2a".sha3(), Some((1, b"1a".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -758,11 +758,11 @@ mod tests {
 		jdb.commit(1, &b"1c".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -826,11 +826,11 @@ mod tests {
 
 		{
 			let mut jdb = EarlyMergeDB::new(dir.to_str().unwrap(), None);
-			assert!(jdb.exists(&foo));
-			assert!(jdb.exists(&bar));
+			assert!(jdb.contains(&foo));
+			assert!(jdb.contains(&bar));
 			jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(!jdb.exists(&foo));
+			assert!(!jdb.contains(&foo));
 		}
 	}
 
@@ -933,7 +933,7 @@ mod tests {
 		jdb.insert(b"foo");
 		jdb.commit(3, &b"3".sha3(), Some((2, b"2".sha3()))).unwrap();	// BROKEN
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.remove(&foo);
 		jdb.commit(4, &b"4".sha3(), Some((3, b"3".sha3()))).unwrap();
@@ -941,7 +941,7 @@ mod tests {
 
 		jdb.commit(5, &b"5".sha3(), Some((4, b"4".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(!jdb.exists(&foo));
+		assert!(!jdb.contains(&foo));
 	}
 
 	#[test]
@@ -1002,12 +1002,12 @@ mod tests {
 			jdb.remove(&foo);
 			jdb.commit(2, &b"2".sha3(), Some((0, b"0".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 
 			jdb.insert(b"foo");
 			jdb.commit(3, &b"3".sha3(), Some((1, b"1".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 
 		// incantation to reopen the db
 		}; { let mut jdb = EarlyMergeDB::new(dir.to_str().unwrap(), None);
@@ -1015,21 +1015,21 @@ mod tests {
 			jdb.remove(&foo);
 			jdb.commit(4, &b"4".sha3(), Some((2, b"2".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 
 		// incantation to reopen the db
 		}; { let mut jdb = EarlyMergeDB::new(dir.to_str().unwrap(), None);
 
 			jdb.commit(5, &b"5".sha3(), Some((3, b"3".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 
 		// incantation to reopen the db
 		}; { let mut jdb = EarlyMergeDB::new(dir.to_str().unwrap(), None);
 
 			jdb.commit(6, &b"6".sha3(), Some((4, b"4".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(!jdb.exists(&foo));
+			assert!(!jdb.contains(&foo));
 		}
 	}
 
@@ -1059,9 +1059,9 @@ mod tests {
 			let mut jdb = EarlyMergeDB::new(dir.to_str().unwrap(), None);
 			jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
-			assert!(!jdb.exists(&baz));
-			assert!(!jdb.exists(&bar));
+			assert!(jdb.contains(&foo));
+			assert!(!jdb.contains(&baz));
+			assert!(!jdb.contains(&bar));
 		}
 	}
 }
diff --git a/util/src/journaldb/overlayrecentdb.rs b/util/src/journaldb/overlayrecentdb.rs
index 709a8fe5f..158b771fb 100644
--- a/util/src/journaldb/overlayrecentdb.rs
+++ b/util/src/journaldb/overlayrecentdb.rs
@@ -288,11 +288,11 @@ impl JournalDB for OverlayRecentDB {
 				}
 				// update the overlay
 				for k in overlay_deletions {
-					journal_overlay.backing_overlay.kill(&k);
+					journal_overlay.backing_overlay.remove(&k);
 				}
 				// apply canon deletions
 				for k in canon_deletions {
-					if !journal_overlay.backing_overlay.exists(&k) {
+					if !journal_overlay.backing_overlay.contains(&k) {
 						try!(batch.delete(&k));
 					}
 				}
@@ -321,12 +321,12 @@ impl HashDB for OverlayRecentDB {
 		ret
 	}
 
-	fn lookup(&self, key: &H256) -> Option<&[u8]> {
+	fn get(&self, key: &H256) -> Option<&[u8]> {
 		let k = self.transaction_overlay.raw(key);
 		match k {
 			Some(&(ref d, rc)) if rc > 0 => Some(d),
 			_ => {
-				let v = self.journal_overlay.read().unwrap().backing_overlay.lookup(key).map(|v| v.to_vec());
+				let v = self.journal_overlay.read().unwrap().backing_overlay.get(key).map(|v| v.to_vec());
 				match v {
 					Some(x) => {
 						Some(&self.transaction_overlay.denote(key, x).0)
@@ -344,8 +344,8 @@ impl HashDB for OverlayRecentDB {
 		}
 	}
 
-	fn exists(&self, key: &H256) -> bool {
-		self.lookup(key).is_some()
+	fn contains(&self, key: &H256) -> bool {
+		self.get(key).is_some()
 	}
 
 	fn insert(&mut self, value: &[u8]) -> H256 {
@@ -354,8 +354,8 @@ impl HashDB for OverlayRecentDB {
 	fn emplace(&mut self, key: H256, value: Bytes) {
 		self.transaction_overlay.emplace(key, value);
 	}
-	fn kill(&mut self, key: &H256) {
-		self.transaction_overlay.kill(key);
+	fn remove(&mut self, key: &H256) {
+		self.transaction_overlay.remove(key);
 	}
 }
 
@@ -397,7 +397,7 @@ mod tests {
 		jdb.commit(6, &b"1005a".sha3(), Some((4, b"1003a".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 
-		assert!(jdb.exists(&x));
+		assert!(jdb.contains(&x));
 	}
 
 	#[test]
@@ -407,20 +407,20 @@ mod tests {
 		let h = jdb.insert(b"foo");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.remove(&h);
 		jdb.commit(1, &b"1".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(2, &b"2".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(3, &b"3".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(4, &b"4".sha3(), Some((1, b"1".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(!jdb.exists(&h));
+		assert!(!jdb.contains(&h));
 	}
 
 	#[test]
@@ -432,38 +432,38 @@ mod tests {
 		let bar = jdb.insert(b"bar");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 
 		jdb.remove(&foo);
 		jdb.remove(&bar);
 		let baz = jdb.insert(b"baz");
 		jdb.commit(1, &b"1".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		let foo = jdb.insert(b"foo");
 		jdb.remove(&baz);
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		jdb.remove(&foo);
 		jdb.commit(3, &b"3".sha3(), Some((2, b"2".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(!jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(!jdb.contains(&baz));
 
 		jdb.commit(4, &b"4".sha3(), Some((3, b"3".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(!jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(!jdb.exists(&baz));
+		assert!(!jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(!jdb.contains(&baz));
 	}
 
 	#[test]
@@ -475,8 +475,8 @@ mod tests {
 		let bar = jdb.insert(b"bar");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 
 		jdb.remove(&foo);
 		let baz = jdb.insert(b"baz");
@@ -487,15 +487,15 @@ mod tests {
 		jdb.commit(1, &b"1b".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&baz));
-		assert!(!jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&baz));
+		assert!(!jdb.contains(&bar));
 	}
 
 	#[test]
@@ -506,19 +506,19 @@ mod tests {
 		let foo = jdb.insert(b"foo");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.remove(&foo);
 		jdb.commit(1, &b"1".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 		jdb.insert(b"foo");
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 		jdb.commit(3, &b"2".sha3(), Some((0, b"2".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -542,11 +542,11 @@ mod tests {
 		jdb.commit(1, &b"1c".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.commit(2, &b"2a".sha3(), Some((1, b"1a".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -570,11 +570,11 @@ mod tests {
 		jdb.commit(1, &b"1c".sha3(), Some((0, b"0".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
 
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 	}
 
 	#[test]
@@ -638,11 +638,11 @@ mod tests {
 
 		{
 			let mut jdb = OverlayRecentDB::new(dir.to_str().unwrap(), None);
-			assert!(jdb.exists(&foo));
-			assert!(jdb.exists(&bar));
+			assert!(jdb.contains(&foo));
+			assert!(jdb.contains(&bar));
 			jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(!jdb.exists(&foo));
+			assert!(!jdb.contains(&foo));
 		}
 	}
 
@@ -745,7 +745,7 @@ mod tests {
 		jdb.insert(b"foo");
 		jdb.commit(3, &b"3".sha3(), Some((2, b"2".sha3()))).unwrap();	// BROKEN
 		assert!(jdb.can_reconstruct_refs());
-		assert!(jdb.exists(&foo));
+		assert!(jdb.contains(&foo));
 
 		jdb.remove(&foo);
 		jdb.commit(4, &b"4".sha3(), Some((3, b"3".sha3()))).unwrap();
@@ -753,7 +753,7 @@ mod tests {
 
 		jdb.commit(5, &b"5".sha3(), Some((4, b"4".sha3()))).unwrap();
 		assert!(jdb.can_reconstruct_refs());
-		assert!(!jdb.exists(&foo));
+		assert!(!jdb.contains(&foo));
 	}
 
 	#[test]
@@ -814,12 +814,12 @@ mod tests {
 			jdb.remove(&foo);
 			jdb.commit(2, &b"2".sha3(), Some((0, b"0".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 
 			jdb.insert(b"foo");
 			jdb.commit(3, &b"3".sha3(), Some((1, b"1".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 
 		// incantation to reopen the db
 		}; { let mut jdb = OverlayRecentDB::new(dir.to_str().unwrap(), None);
@@ -827,21 +827,21 @@ mod tests {
 			jdb.remove(&foo);
 			jdb.commit(4, &b"4".sha3(), Some((2, b"2".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 
 		// incantation to reopen the db
 		}; { let mut jdb = OverlayRecentDB::new(dir.to_str().unwrap(), None);
 
 			jdb.commit(5, &b"5".sha3(), Some((3, b"3".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
+			assert!(jdb.contains(&foo));
 
 		// incantation to reopen the db
 		}; { let mut jdb = OverlayRecentDB::new(dir.to_str().unwrap(), None);
 
 			jdb.commit(6, &b"6".sha3(), Some((4, b"4".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(!jdb.exists(&foo));
+			assert!(!jdb.contains(&foo));
 		}
 	}
 
@@ -871,9 +871,9 @@ mod tests {
 			let mut jdb = OverlayRecentDB::new(dir.to_str().unwrap(), None);
 			jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
 			assert!(jdb.can_reconstruct_refs());
-			assert!(jdb.exists(&foo));
-			assert!(!jdb.exists(&baz));
-			assert!(!jdb.exists(&bar));
+			assert!(jdb.contains(&foo));
+			assert!(!jdb.contains(&baz));
+			assert!(!jdb.contains(&bar));
 		}
 	}
 
@@ -893,7 +893,7 @@ mod tests {
 		assert!(jdb.can_reconstruct_refs());
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
 
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 	}
 }
diff --git a/util/src/journaldb/refcounteddb.rs b/util/src/journaldb/refcounteddb.rs
index 31f31f654..fc7da1541 100644
--- a/util/src/journaldb/refcounteddb.rs
+++ b/util/src/journaldb/refcounteddb.rs
@@ -88,11 +88,11 @@ impl RefCountedDB {
 
 impl HashDB for RefCountedDB {
 	fn keys(&self) -> HashMap<H256, i32> { self.forward.keys() }
-	fn lookup(&self, key: &H256) -> Option<&[u8]> { self.forward.lookup(key) }
-	fn exists(&self, key: &H256) -> bool { self.forward.exists(key) }
+	fn get(&self, key: &H256) -> Option<&[u8]> { self.forward.get(key) }
+	fn contains(&self, key: &H256) -> bool { self.forward.contains(key) }
 	fn insert(&mut self, value: &[u8]) -> H256 { let r = self.forward.insert(value); self.inserts.push(r.clone()); r }
 	fn emplace(&mut self, key: H256, value: Bytes) { self.inserts.push(key.clone()); self.forward.emplace(key, value); }
-	fn kill(&mut self, key: &H256) { self.removes.push(key.clone()); }
+	fn remove(&mut self, key: &H256) { self.removes.push(key.clone()); }
 }
 
 impl JournalDB for RefCountedDB {
@@ -212,16 +212,16 @@ mod tests {
 		let mut jdb = RefCountedDB::new_temp();
 		let h = jdb.insert(b"foo");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.remove(&h);
 		jdb.commit(1, &b"1".sha3(), None).unwrap();
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(2, &b"2".sha3(), None).unwrap();
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(3, &b"3".sha3(), Some((0, b"0".sha3()))).unwrap();
-		assert!(jdb.exists(&h));
+		assert!(jdb.contains(&h));
 		jdb.commit(4, &b"4".sha3(), Some((1, b"1".sha3()))).unwrap();
-		assert!(!jdb.exists(&h));
+		assert!(!jdb.contains(&h));
 	}
 
 	#[test]
@@ -251,34 +251,34 @@ mod tests {
 		let foo = jdb.insert(b"foo");
 		let bar = jdb.insert(b"bar");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 
 		jdb.remove(&foo);
 		jdb.remove(&bar);
 		let baz = jdb.insert(b"baz");
 		jdb.commit(1, &b"1".sha3(), Some((0, b"0".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		let foo = jdb.insert(b"foo");
 		jdb.remove(&baz);
 		jdb.commit(2, &b"2".sha3(), Some((1, b"1".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		jdb.remove(&foo);
 		jdb.commit(3, &b"3".sha3(), Some((2, b"2".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(!jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(!jdb.contains(&baz));
 
 		jdb.commit(4, &b"4".sha3(), Some((3, b"3".sha3()))).unwrap();
-		assert!(!jdb.exists(&foo));
-		assert!(!jdb.exists(&bar));
-		assert!(!jdb.exists(&baz));
+		assert!(!jdb.contains(&foo));
+		assert!(!jdb.contains(&bar));
+		assert!(!jdb.contains(&baz));
 	}
 
 	#[test]
@@ -289,8 +289,8 @@ mod tests {
 		let foo = jdb.insert(b"foo");
 		let bar = jdb.insert(b"bar");
 		jdb.commit(0, &b"0".sha3(), None).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
 
 		jdb.remove(&foo);
 		let baz = jdb.insert(b"baz");
@@ -299,13 +299,13 @@ mod tests {
 		jdb.remove(&bar);
 		jdb.commit(1, &b"1b".sha3(), Some((0, b"0".sha3()))).unwrap();
 
-		assert!(jdb.exists(&foo));
-		assert!(jdb.exists(&bar));
-		assert!(jdb.exists(&baz));
+		assert!(jdb.contains(&foo));
+		assert!(jdb.contains(&bar));
+		assert!(jdb.contains(&baz));
 
 		jdb.commit(2, &b"2b".sha3(), Some((1, b"1b".sha3()))).unwrap();
-		assert!(jdb.exists(&foo));
-		assert!(!jdb.exists(&baz));
-		assert!(!jdb.exists(&bar));
+		assert!(jdb.contains(&foo));
+		assert!(!jdb.contains(&baz));
+		assert!(!jdb.contains(&bar));
 	}
 }
diff --git a/util/src/memorydb.rs b/util/src/memorydb.rs
index cfd7237e6..ea77f4aa2 100644
--- a/util/src/memorydb.rs
+++ b/util/src/memorydb.rs
@@ -162,7 +162,7 @@ impl MemoryDB {
 static NULL_RLP_STATIC: [u8; 1] = [0x80; 1];
 
 impl HashDB for MemoryDB {
-	fn lookup(&self, key: &H256) -> Option<&[u8]> {
+	fn get(&self, key: &H256) -> Option<&[u8]> {
 		if key == &SHA3_NULL_RLP {
 			return Some(&NULL_RLP_STATIC);
 		}
@@ -176,7 +176,7 @@ impl HashDB for MemoryDB {
 		self.data.iter().filter_map(|(k, v)| if v.1 != 0 {Some((k.clone(), v.1))} else {None}).collect()
 	}
 
-	fn exists(&self, key: &H256) -> bool {
+	fn contains(&self, key: &H256) -> bool {
 		if key == &SHA3_NULL_RLP {
 			return true;
 		}
@@ -222,7 +222,7 @@ impl HashDB for MemoryDB {
 		self.data.insert(key, (value, 1));
 	}
 
-	fn kill(&mut self, key: &H256) {
+	fn remove(&mut self, key: &H256) {
 		if key == &SHA3_NULL_RLP {
 			return;
 		}
diff --git a/util/src/overlaydb.rs b/util/src/overlaydb.rs
index ce4e894c8..b1ea44dac 100644
--- a/util/src/overlaydb.rs
+++ b/util/src/overlaydb.rs
@@ -92,7 +92,7 @@ impl OverlayDB {
 	///
 	/// Returns either an error or the number of items changed in the backing database.
 	///
-	/// Will return an error if the number of `kill()`s ever exceeds the number of
+	/// Will return an error if the number of `remove()`s ever exceeds the number of
 	/// `insert()`s for any key. This will leave the database in an undeterminate
 	/// state. Don't ever let it happen.
 	///
@@ -104,15 +104,15 @@ impl OverlayDB {
 	/// fn main() {
 	///   let mut m = OverlayDB::new_temp();
 	///   let key = m.insert(b"foo");			// insert item.
-	///   assert!(m.exists(&key));				// key exists (in memory).
+	///   assert!(m.contains(&key));			// key exists (in memory).
 	///   assert_eq!(m.commit().unwrap(), 1);	// 1 item changed.
-	///   assert!(m.exists(&key));				// key still exists (in backing).
-	///   m.kill(&key);							// delete item.
-	///   assert!(!m.exists(&key));				// key "doesn't exist" (though still does in backing).
-	///   m.kill(&key);							// oh dear... more kills than inserts for the key...
+	///   assert!(m.contains(&key));			// key still exists (in backing).
+	///   m.remove(&key);							// delete item.
+	///   assert!(!m.contains(&key));			// key "doesn't exist" (though still does in backing).
+	///   m.remove(&key);							// oh dear... more removes than inserts for the key...
 	///   //m.commit().unwrap();				// this commit/unwrap would cause a panic.
-	///   m.revert();							// revert both kills.
-	///   assert!(m.exists(&key));				// key now still exists.
+	///   m.revert();							// revert both removes.
+	///   assert!(m.contains(&key));			// key now still exists.
 	/// }
 	/// ```
 	pub fn commit(&mut self) -> Result<u32, UtilError> {
@@ -224,7 +224,7 @@ impl HashDB for OverlayDB {
 		}
 		ret
 	}
-	fn lookup(&self, key: &H256) -> Option<&[u8]> {
+	fn get(&self, key: &H256) -> Option<&[u8]> {
 		// return ok if positive; if negative, check backing - might be enough references there to make
 		// it positive again.
 		let k = self.overlay.raw(key);
@@ -249,7 +249,7 @@ impl HashDB for OverlayDB {
 			}
 		}
 	}
-	fn exists(&self, key: &H256) -> bool {
+	fn contains(&self, key: &H256) -> bool {
 		// return ok if positive; if negative, check backing - might be enough references there to make
 		// it positive again.
 		let k = self.overlay.raw(key);
@@ -271,7 +271,7 @@ impl HashDB for OverlayDB {
 	}
 	fn insert(&mut self, value: &[u8]) -> H256 { self.overlay.insert(value) }
 	fn emplace(&mut self, key: H256, value: Bytes) { self.overlay.emplace(key, value); }
-	fn kill(&mut self, key: &H256) { self.overlay.kill(key); }
+	fn remove(&mut self, key: &H256) { self.overlay.remove(key); }
 }
 
 #[test]
diff --git a/util/src/trie/triedb.rs b/util/src/trie/triedb.rs
index fccd5da90..9cd3a8c41 100644
--- a/util/src/trie/triedb.rs
+++ b/util/src/trie/triedb.rs
@@ -133,7 +133,7 @@ impl<'db> TrieDB<'db> {
 
 	/// Get the data of the root node.
 	fn root_data(&self) -> &[u8] {
-		self.db.lookup(&self.root).expect("Trie root not found!")
+		self.db.get(&self.root).expect("Trie root not found!")
 	}
 
 	/// Get the root node as a `Node`.
@@ -184,7 +184,7 @@ impl<'db> TrieDB<'db> {
 
 	/// Return optional data for a key given as a `NibbleSlice`. Returns `None` if no data exists.
 	fn do_lookup<'a, 'key>(&'a self, key: &NibbleSlice<'key>) -> Option<&'a [u8]> where 'a: 'key {
-		let root_rlp = self.db.lookup(&self.root).expect("Trie root not found!");
+		let root_rlp = self.db.get(&self.root).expect("Trie root not found!");
 		self.get_from_node(&root_rlp, key)
 	}
 
@@ -213,7 +213,7 @@ impl<'db> TrieDB<'db> {
 		// check if its sha3 + len
 		let r = Rlp::new(node);
 		match r.is_data() && r.size() == 32 {
-			true => self.db.lookup(&r.as_val::<H256>()).unwrap_or_else(|| panic!("Not found! {:?}", r.as_val::<H256>())),
+			true => self.db.get(&r.as_val::<H256>()).unwrap_or_else(|| panic!("Not found! {:?}", r.as_val::<H256>())),
 			false => node
 		}
 	}
@@ -349,7 +349,7 @@ impl<'db> Trie for TrieDB<'db> {
 impl<'db> fmt::Debug for TrieDB<'db> {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		try!(writeln!(f, "c={:?} [", self.hash_count));
-		let root_rlp = self.db.lookup(&self.root).expect("Trie root not found!");
+		let root_rlp = self.db.get(&self.root).expect("Trie root not found!");
 		try!(self.fmt_all(Node::decoded(root_rlp), f, 0));
 		writeln!(f, "]")
 	}
diff --git a/util/src/trie/triedbmut.rs b/util/src/trie/triedbmut.rs
index afabd6437..65d5bbd2b 100644
--- a/util/src/trie/triedbmut.rs
+++ b/util/src/trie/triedbmut.rs
@@ -87,7 +87,7 @@ impl<'db> TrieDBMut<'db> {
 	/// Create a new trie with the backing database `db` and `root`.
 	/// Returns an error if `root` does not exist.
 	pub fn from_existing(db: &'db mut HashDB, root: &'db mut H256) -> Result<Self, TrieError> {
-		if !db.exists(root) {
+		if !db.contains(root) {
 			Err(TrieError::InvalidStateRoot)
 		} else {
 			Ok(TrieDBMut {
@@ -143,7 +143,7 @@ impl<'db> TrieDBMut<'db> {
 	/// Set the trie to a new root node's RLP, inserting the new RLP into the backing database
 	/// and removing the old.
 	fn set_root_rlp(&mut self, root_data: &[u8]) {
-		self.db.kill(&self.root);
+		self.db.remove(&self.root);
 		*self.root = self.db.insert(root_data);
 		self.hash_count += 1;
 		trace!("set_root_rlp {:?} {:?}", root_data.pretty(), self.root);
@@ -174,7 +174,7 @@ impl<'db> TrieDBMut<'db> {
 
 	/// Get the root node's RLP.
 	fn root_node(&self) -> Node {
-		Node::decoded(self.db.lookup(&self.root).expect("Trie root not found!"))
+		Node::decoded(self.db.get(&self.root).expect("Trie root not found!"))
 	}
 
 	/// Get the root node as a `Node`.
@@ -225,7 +225,7 @@ impl<'db> TrieDBMut<'db> {
 
 	/// Return optional data for a key given as a `NibbleSlice`. Returns `None` if no data exists.
 	fn do_lookup<'a, 'key>(&'a self, key: &NibbleSlice<'key>) -> Option<&'a [u8]> where 'a: 'key {
-		let root_rlp = self.db.lookup(&self.root).expect("Trie root not found!");
+		let root_rlp = self.db.get(&self.root).expect("Trie root not found!");
 		self.get_from_node(&root_rlp, key)
 	}
 
@@ -254,7 +254,7 @@ impl<'db> TrieDBMut<'db> {
 		// check if its sha3 + len
 		let r = Rlp::new(node);
 		match r.is_data() && r.size() == 32 {
-			true => self.db.lookup(&r.as_val::<H256>()).expect("Not found!"),
+			true => self.db.get(&r.as_val::<H256>()).expect("Not found!"),
 			false => node
 		}
 	}
@@ -266,7 +266,7 @@ impl<'db> TrieDBMut<'db> {
 		trace!("ADD: {:?} {:?}", key, value.pretty());
 		// determine what the new root is, insert new nodes and remove old as necessary.
 		let mut todo: Journal = Journal::new();
-		let root_rlp = self.augmented(self.db.lookup(&self.root).expect("Trie root not found!"), key, value, &mut todo);
+		let root_rlp = self.augmented(self.db.get(&self.root).expect("Trie root not found!"), key, value, &mut todo);
 		self.apply(todo);
 		self.set_root_rlp(&root_rlp);
 		trace!("/");
@@ -279,7 +279,7 @@ impl<'db> TrieDBMut<'db> {
 		trace!("DELETE: {:?}", key);
 		// determine what the new root is, insert new nodes and remove old as necessary.
 		let mut todo: Journal = Journal::new();
-		match self.cleared_from_slice(self.db.lookup(&self.root).expect("Trie root not found!"), key, &mut todo) {
+		match self.cleared_from_slice(self.db.get(&self.root).expect("Trie root not found!"), key, &mut todo) {
 			Some(root_rlp) => {
 				self.apply(todo);
 				self.set_root_rlp(&root_rlp);
@@ -335,7 +335,7 @@ impl<'db> TrieDBMut<'db> {
 		}
 		else if rlp.is_data() && rlp.size() == 32 {
 			let h = rlp.as_val();
-			let r = self.db.lookup(&h).unwrap_or_else(||{
+			let r = self.db.get(&h).unwrap_or_else(||{
 				println!("Node not found! rlp={:?}, node_hash={:?}", rlp.as_raw().pretty(), h);
 				println!("Journal: {:?}", journal);
 				panic!();
@@ -670,7 +670,7 @@ impl<'db> TrieMut for TrieDBMut<'db> {
 impl<'db> fmt::Debug for TrieDBMut<'db> {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 		try!(writeln!(f, "c={:?} [", self.hash_count));
-		let root_rlp = self.db.lookup(&self.root).expect("Trie root not found!");
+		let root_rlp = self.db.get(&self.root).expect("Trie root not found!");
 		try!(self.fmt_all(Node::decoded(root_rlp), f, 0));
 		writeln!(f, "]")
 	}