Green’s Dictionary of Slang

duff n.3

In phrases

up the duff (adj.) [SE duff, a pudding, same imagery as have a bun in the oven under oven n.; pudding club n.]

(orig. Aus.) pregnant; thus rhy. sl. up the Damien (duff).

[Aus]Baker Popular Dict. Aus. Sl.
‘Down the Dark Alley’ in Mess Songs & Rhymes of RAAF 1939-45 [Internet] Buff. I put her up the duff.
[Aus]B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 36: I don’t like long haired pommy bastards who get nice sheilahs up the duff and then shoot through.
[UK]J. Gaskell All Neat in Black Stockings 148: He’d seen a few other birds up the duff claiming I was the father.
[Aus]A. Buzo Rooted III iii: Hope you don’t pick up a dose or put her up the duff.
[NZ]P. Wilson N.Z. Jack 124: Do you want to get her up the flaming duff?
[UK](con. 1940s) I. Agnew Loner 133: She said to tell you she’s up the duff to a Maori.
[UK]J. Sullivan ‘From Prussia With Love’ Only Fools and Horses [TV script] Unless I’m very much mistaken that young girl out there’s up the duff.
[Aus]C. Bowles G’DAY 27: Mr Foster is at the table [...] Darlene is sitting next to him, quietly. She's just discovered she's up the duff.
[UK]I. Welsh Filth 6: Some cunt’ll knock her up the duff.
[UK]Guardian Guide 4–10 Sept. 12: Carol was at it again [...] up the duff, and with hunky playboy Dan.
[UK]M. Manning Get Your Cock Out 49: It’s my lady, man, Guinevere, she’s up the duff.
[UK]Indep. on Sun. Rev. 16 Dec. 17: So now Milly Molly Mandy / Gets up the duff for feeling randy.
[UK]Guardian G2 28 Dec. 14: She runs away to shack up with her new bit of rough [...] It’s not long before she’s up the duff.
[Ire]P. Howard Curious Incident of the Dog in the Nightdress 4: Sorcha’s not the only one who’s surprised I got her up the Damien.
[UK]Daily Mirror 10 Jan. 33: [She] finally announced she’s up the duff.
[Aus]L. Redhead Thrill City [ebook] ‘Your tits are huge.’ [...] ‘I am up the duff’.
[UK](con. 1980s) I. Welsh Skagboys 163: An awfay loat ay fuss aboot some fuckin slag gittin up the duff.
[UK]V. McDermid Out of Bounds (2017) 322: ‘He got her up the duff, then legged it’.
[Aus]T. Spicer Good Girl Stripped Bare 70: ‘I’m her sister [...] He’s got me up the duff, too’.