Green’s Dictionary of Slang

1. fake, spurious.

1877		Five Years’ Penal Servitude 239: Sure enough [the coins] were a ‘shise’ half-bull and a ‘duffing’ [i.e. ‘duff ’un’].
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.].
1910		Sessions Papers CLIV. 24 Nov. 82: I rang it [i.e. a coin] on the counter; he said ‘Break it up it is duff.’.
1944		P. Kendall Dict. Service Sl. n.p.: duff gen . . . rumors.
1960		C. MacInnes Mr Love and Justice (1964) 191: I’ve thought of trying: stow away and get duff papers.
1979		J. Morrow Confessions of Proinsias O’Toole 124: The two duff letters lay on the bedside table.
1981		(con. c.1920) A. Harding in Samuel East End Und. 92: They was on ‘duff’ photos – they took a picture, got the deposit on them and they never developed the prints.
1989		J. Morton Lowspeak 53: Duff [...] incorrect, as in ‘All he does is give duff info’.

2. (also duffed, duffin, duffing) of objects, useless, broken down, inferior.

1878		‘’Arry at the Play’ in Punch 2 Nov. in P. Marks (2006) 39: I thought theayter cold muffin / And SHAKESPEAR and BYRON and them on the ’ole is decidedly duffin.
1884		Sporting Times 5 jan. 1/1: After each had tried to gulp down a glass, Jemmy said, ‘Well, Ned what do you think of it [i.e. ‘champagne’] . Ned answered, ‘It’s duffing, Jemmy’.
1935		(con. 1920s) McArthur & Long No Mean City 110: I’ve seen your kind before [...] readin’ books and newspapers; winchin’ brainy bit stuffs wi’ good clothes over a duff figure.
1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 4: Duff stuff: No good.
1936		I.L. Idriess Cattle King 90: Those horses you sold me are all duffed. I want my money back.
1938		J. Curtis They Drive by Night 47: Duff old machines these.
1958		F. Norman Bang To Rights 136: I bought six cars last week [...] and four of them are duff.
1959		W. Hall Long and the Short and the Tall Act I: Damn duff equipment! The whole damn issue’s duff.
1971		(con. WWII) B. Aldiss Soldier Erect 188: They’ll have that duff head of yours cut off as soon as look at it.
1972		P. Fordham Inside the Und. 39: A duff docket was signed.
1981		P. Wright Cockney Dialect and Sl. 93: A firm may get a delivery of duff (faulty) records.
1999		Indep. Rev. 16 Oct. 9: It seems entirely unjust that so decent a soul should have been dealt some duff cards.
2004		posting at www.anchorbay.co.uk 30 Jan. 🌐 I wasn’t the only one to receive a duff copy of ‘Pulp Fiction’.

3. of people, inadequate, incompetent.

1938		G. Kersh Night and the City 233: You duff wrestler! You great big palooka!
1941		G. Kersh They Die with Their Boots Clean 125: I’ve seen Bullock fight twice [...] he’s duff. he’s terrible.
1956		J. Curtis Look Long Upon a Monkey 187: You’re a good ’un all right, but you picked a duff team to go to work with.
1962		A. Wesker Chips with Everything II x: You poor duff bastards, where are your mothers?
1999		Guardian Rev. 12 June 8: The bum notes of dialogue, the duff characters.