Green’s Dictionary of Slang

1. easy, simple, lucky, profitable [jam n.² (1a)].

1889		Dead Bird (Sydney) 21 Sept. 3/2: In a well-known town [...] resides a hearty publican [...] He is a real ‘jammy’ lot, and no humbug about him.
1899		Kipling ‘The Last Term’ in Complete Stalky & Co. (1987) 266: Jam for the Sixth! Jam for us! Either way it’s jammy!
1905		T.A. Dorgan in Zwilling TAD Lex. (1993) 50: Yes he’s the citron we’ll have to hand to the boy. The real Jammy article put up only in can’s with our name on the wrapper.
1917		W. Muir Observations of Orderly 229: A few other slang words which I have come across in the hospital, and which seem to me to bear the mark of the old army as distinct from the new are: [...] ‘jammy,’ lucky (and ‘jam,’ any sort of good fortune).
1922		‘J.H. Ross’ Mint (1955) 69: The clerks lounged with their first cups of tea. ‘Jammy cunts,’ sneered Sailor enviously.
1938		J. Curtis They Drive by Night 74: Bit of all right to be there instead of freezing to death along the Great North Road. Jammy.
1943		M. Harrison Reported Safe Arrival 50: I reckon this is goin’ ter be jammy.
1959		K. Waterhouse Billy Liar (1962) 51: Jammy bugger!
1962		K. Waterhouse There is a Happy Land (1964) 100: Oo, lucky you! Dead jammy!
1963		C. Wood ‘Prisoner and Escort’ in Cockade (1965) I iii: Jammy [...] Piece of cake.
1977		(con. 1961) J. Rosenthal Spend, Spend, Spend Scene 17: Some jammy pig’s won a million pounds.
1989		M. Amis London Fields 378: I’m just a jammy bastard, according to some.
1996		P. Howard The Joy (2015) [ebook] Me and Dekker scored a couple of turn-ons each and Mick, the jammy cunt, had enough for five.
1999		Indep. Rev. 5 July 8: The groom was a ‘spoilt brat’ and a ‘jammy bastard’.
2005		B. Hare Urban Grimshaw 206: You jammy little bastard.
2021		L. McInerney Rules of Revelation 115: S‘he always said i was a jammy prick’.

2. (Aus./US) pretentious; self-satisfied [jam n.² (2a)].

1899		Independent (Honolulu) 13 Jan. 2/2: S is for Smith, also for Sammy / Both with smiles so bland and jammy.
1905		Bulletin (Sydney) 9 Nov. 14/1: I got a letter from the inspector. He must ’a’ been sober when he wrote, because usually what you could read of his letters was real ’jammy.‘.
1913		Sport (Adelaide) 26 July 10/3: Sanchy R., the jammy boy, was down at the Outer Harbor [...] Leave the babies alone, Sanch, and get a girl.
1921		(con. WWI) E. Lynch Somme Mud 71: He seems [...] a little too jammy in speech to become over popular with our crowd. They will stand a lot of anything, but very little of anything that they look upon as affectation .

3. bloodsoaked [? jam n.² (4b)].

1914

E. Packe letter 27 Sept. 🌐 One of our officers noticed that his haversack was bulging very much and also was very ‘jammy’.