Green’s Dictionary of Slang

the anus, the buttocks, the vagina or penis; thus up the kazoo, either lit. ‘up the arse’ or implying completeness or excess, e.g. I’ve got customers up the kazoo.

1968		A. Burgess Enderby Outside in Complete Enderby (2002) 365: There’d them shoving it up the old kazerzy [...] very painful.
1972		B.J. Friedman Steambath n.p.: He made this big blow-up of her private parts . . . everybody looking up her old kazoo [R].
1972		D. Pendleton Boston Blitz (1974) 126: They’re handing out indictments up the kazoo.
1978		S. King Stand (1990) 467: You’ll all come back with [...] a good case of poison ivy up the kazoo from shitting in the woods.
1987		A. Simpson 19 Mar. n.p.: You’re asking him things because you know he’s off-balance and you’d like to stick it in his kazoo [R].
1993		S. King Dolores Claiborne 4: Oh, frig ya coffee! Take the whole pot and shove it up your kazoo.
1997		Mad mag. June 45: See how we do ya, / Stick it right to ya, / All the way up the ka-zoo!
2000		W.T. Vollmann Royal Family 663: The guy is in trouble [...] Felonies up the kazebo.
2002		S. Maloney Something Fishy (2006) 156: I was wedged [...] the blade of an oar jammed up my kazoo.
2019		Twitter 21 July 🌐 I wouldn’t say no to a little more diversity in the area of FILM. You know, maybe some movies without superheroes or CGI up the kazoo.