The knock-knock joke
Knock knock.
Who's there?
Boo.
Boo who?
Don't cry, it's only a joke.
Who told it first?
Origin unknown (folk joke)
Nobody knows who told it first.
Nobody has been shown to have invented it. The earliest firm evidence is the 1936 craze; older "knocking at the door" exchanges exist but are not the same joke.
Older versions, rival claims and what came next
- c. 1597 older relative Ben Jonson - The play The Case is Altered has an exchange with a knock-knock feel. A loose ancestor, not the joke.
- 1606 older relative Shakespeare - The porter scene in Macbeth opens with knocking and "who's there". A loose antecedent only.
- c. 1900 claim Merely McEvoy (Oakland Tribune) - A columnist later recalled a name-and-punchline joke of this pattern from about 1900. A recollection, not a dated print source.
- 1929 older relative Henry Bett, The Games of Children - Describes a children's game ("Buff") with a knock-knock style dialogue.
- 1936-08-03 documented Associated Press (reprinted in the Boston Globe) - Reports the joke had replaced another parlor game as a favourite. Knock-knock clubs formed in the Midwest that year. source
- 1936-12-30 claim Fred Allen (radio) - Joked that a man called Ramrod Dank invented it. A gag, not history.
Sources
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