Who Invented the Skeleton Key, How Did the Passkey Get its Name, and Where Did the Skeleton Key Come From?

A “master key” is designed to open a specific set of several locks.

Although these locks have individual keys, they also have a second tumbler system within the mechanism that enables the master key to open any one within that set.

A “skeleton key” is a key ground down by criminals to pick a lock by avoiding the wards in a warded lock.

Warded locks are those opened with a long-stem cylindrical shaft with a single flat rectangular tooth and are mostly out of fashion.

They were called skeleton keys because they had been filed down to the “bare bones.”

An underworld slang term for a skeleton key is screw, which is why convicts call guards in a prison “screws”, because they carry the keys.