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1904 Daily Chron. 2 July 8/1 The knock-knocking at the door sending a thrill through the pulse.

1936 Variety 19 Aug. 25/5 Manager Russell Bovim, of Loew's Broad, Columbus, cashed in handsomely on the ‘Knock Knock’ craze now sweeping the country.

1941 C. Graves Life Line 179 Certain trawlers have the job of sweeping for magnetic mines (known as ‘Maggies’) and the latest acoustic mines (known as ‘knock-knocks’).

1957 O. Nash You can't get there from Here 151 Who, rapped Mr. Webster, escapes an escapee? That, knock-knocked Mr. Merriam, is what puzzles me.

1959 I. Opie & P. Opie Lore & Lang. Schoolchildren v. 82 A craze for Wellerisms is apt to develop in a school in the same way that there are still sometimes crazes for limericks, Little Audrey jokes, Knock-knocks, and Shaggy-dog stories.

1961 E. Partridge Dict. Slang (ed. 5) II. 1161/1 Knock! knock! A c.p., dating from the middle of Nov. 1936... Orig. ex U.S. It is used, esp. among busmen, by a person about to tell a dirty story or, esp., to make a pun, gen. in doubtful taste.

1974 Radio Times 19 Oct. 59 ‘Knock, knock.’ ‘Who's there?’ ‘Richard Milhous.’ ‘Richard Milhous who?’ ‘Ah…how quickly people forget.’