The person who expressed criticism has similar faults to the person being criticized. This classic retort to an insult dates from the early 1900s. For example, You say she's a terrible cook? It takes one to know one! For a synonym, see pot calling the kettle black A near equivalent is the proverbialit takes a thief to catch a thief, meaning “no one is better at finding a wrongdoer than another wrongdoer.” First recorded in 1665, it remains current.