Green’s Dictionary of Slang

duff n.2

[west Yorks. dial. duff, the posterior]

1. the buttocks.

[UK] ‘Kiss My Duff’ in Secret Songster 19: I never takes no mummery. / ’Cause I’m a regular – ‘kiss my duff’.
[UK] ‘Rare Old Root’ in Cuckold’s Nest 9: It’s seen many ruffs and pretty white duffs, / And has long been exposed to h-air.
[UK] ‘Nancy Dawson’ in Nancy Dawson’s Cabinet of Songs 11: Her duff she up and down did jerk.
[UK] ‘Last Dying Speech . . . of the Lord Mayor’s Show’ in C. Hindley Curiosities of Street Lit. (1871) 145: And he has broke his sword on the old donkey’s duff.
[UK]G.F. Northall Folk-Phrases of Four Counties 26: To be down on one’s duff. i.e. down on one’s luck; or in the dumps.
[US](con. late 19C) N. Kimball Amer. Madam (1981) 191: There’s nothing we can do, dearie, but sit on our duff and wait.
[US]G. McMillan Old Breed 408: Those old buzzards have been sittin’ on their duff at desks!
[US](con. 1950) E. Frankel Band of Brothers 46: How am I gonna get that Congressional sitting on my duff in the CP?
[US]E. Bombeck At Wit’s End (1979) 206: You’d think some man would get off his duff and give a woman a seat.
[US]S. Longstreet Straw Boss (1979) 251: I’m not sitting on my duff.
[US]J. Ciardi Good Words 96: Duff. The ass. One’s rear end.
[US]C. Hiaasen Skinny Dip 240: Sitting on their flabby duffs doing nothing.
[US]J. Stahl Bad Sex on Speed 102: Narcolepsy, my fat musty duff [...] They give uis speed cause we’re bored.

2. the vagina.

[UK]‘Walter’ My Secret Life (1966) I 172: Our conversation used to begin by my saying, ‘How’s your duff?’ ‘Oh, nicely, thank you; how is your jock?’ ‘All right and stiff, waiting for your duff.’.

In compounds

duff-flogger (n.)

(US) a male masturbator.

[US]N. Kimball Amer. Madam (1981) 310: In Washington D.C., there is a law against masturbation that could lead a duff-flogger to a prison term.

In phrases

duff around (v.)

to sit about, to act lazily.

P. Mattingly ‘Branded and Roped’ at [Internet] After he left and we were sure he couldn’t hear us duff around, every Taylor in there was being strummed. We didn’t sound like him.
shoot one’s duff (v.)

to ejaculate.

[UK](con. 1980s) I. Welsh Skagboys 76: Once ah’ve shot ma duff ower the threadbare broon couch, ah feel a bit low.