Green’s Dictionary of Slang

(orig. US) to perform cunnilingus.

c.1930		(ref. late 19C) N. Kimball Amer. Madam (1981) 89: These items of sexual life had various names over the years. [...] If the guest was the active partner, he was muff-diving, a face-man, or after sea-food-mama.
1948		in G. Legman Limerick (1953) 86: She said, ‘When you muff-dive on / The living-room divan. / Please use an anti-macassar.’.
1988		H. Max Gay (S)language.
1990		(con. early 1950s) J. Ellroy L.A. Confidential 178: Snapshots [...] Tallulah Bankhead muff-diving.
2000		M. Manning Get Your Cock Out 86: The two lovers buggered, fellated, fucked, wanked and muffdived till the dawn’s early light slid through the holes in Mincey’s filthy curtains.
2003		K. Cage Gayle.
2021		J. Ellroy Widespread Panic 5: ‘He’s muff-diving a three-hundred pound chick. That was a boss beef, back in ’51’.