nouninformal, rare, historical
(A generic name for) an executioner or hangman.
Late 17th century. From the name of Jack Ketch (d. 1686), public executioner in London, known in particular for his executions of William, Lord Russell and James Scott, Duke of Monmouth. From the 18th century, the name was also used for the character of the hangman in the Punch and Judy show.