subs. phr. (common).—A key: formerly the key with which the doors of sponging-houses were unlocked: also LOCKSMITH’S DAUGHTER.
1859. DICKENS, Tale of Two Cities. Place it under the care of the BLACKSMITH’S DAUGHTER.
1864. Reader [quoted in Notes and Queries, 5 S., ix., 263]. BLACKSMITH’S DAUGHTER. A key. I have never met with this word in print, but have heard it frequently in conversation.
