Green’s Dictionary of Slang

1. good, excellent.

1796		Grose Classical Dict. of the Vulgar Tongue (3rd edn) n.p.: It is all plummy; i.e. all is right, or as it ought to be.
1812		Vaux Vocab. of the Flash Lang. in McLachlan (1964) 258: plummy Right; very good; as it should be; expressing your approbation or any act, or event, you will say, That’s plummy, or It’s all plummy; meaning it is alright.
1830		W.T. Moncrieff Heart of London III ii: Nothing could be more plummy! twenty thousand pounds.
1838		R. Nicholson Cockney Adventures 24 Feb. 131: ‘How plummy!’ said Ben Gubbins. [Ibid.] 3 Mar. 139: The delighted young man gave a kind of ecstatic spring into the air, which he accompanied with the school-boy ejaculation of ‘Oh, how plummy!’.
1841		‘Hurrah For An Irish Stew’ Dublin Comic Songster 100: Hurrah! for an Irish stew. / It’s plummy wid pepper and salt.
1842		Whip & Satirist of NY & Brooklyn (NY) 12 Mar. n.p.: The schoolboy expression of ‘Oh, how plummy’.
1853		Delhi Sketch Bk 1 Oct. 67: [cartoon caption] Come, Judge, Have a Turn, It’s so Plummy!
1856		‘A Harassing Painsworth’ in Yates & Brough (eds) Our Miscellany 28: ‘And now,’ said the latter, ‘now that all’s plummy and slam, let’s have your jaw’.
1859		‘Scene in a London Flash-Panny’ Matsell Vocabulum 100: ‘Oh! it’s all plummy,’ said Knapp, ‘so you may cly your daddles.’.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor II 123/1: The pickles – cowcumbers is best – are stunning. But they’re plummiest with a bit of cheese. [Ibid.] III 408/1: The bread’s fine, Joe; but the sleep, isn’t that plummy?
1876		‘George Eliot’ Daniel Deronda (1967) 223: The poets have made tragedies enough about signing oneself over to wickedness for the sake of getting something plummy.
1983		B. Gelb Vanished Brass 120: [T]he plummiest field job in the department, the Manhattan South area.

2. round, sleek, fat, jolly.

1842		Boston Satirist (MA) 21 Oct. n.p.: Joan was beauty’s plummiest daughter, / Colin youth’s most nutty son.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1873		Sl. Dict.
1890		Bulletin (Sydney) 9 Aug. 15/2: There is a school not a thousand miles from the ‘City of the Plains,’ in the South Island of N.Z., where the lady-teacher is of the ‘plummy’ type of build.
1905		‘Doss Chiderdoss’ ‘A Polyglot Policeman’ Sporting Times 1 Apr. 1/4: That plummy little nursemaid who’s at number twenty-three, / German Gretchen, in whose praise I’ve often sung, / Smiled upon me till that rozzer came, and now it’s all U P.

3. of a voice, affected or upper-class; thus of a person, plummy-voiced [SE have a plum in the mouth].

1843		R.S. Surtees Handley Cross (1854) 174: ‘Make vay for the real swells vot pay!’ roared a stentorian voice [...] ‘There’s a brace of plummy ones;’ exclaimed another.
1853		R.S. Surtees Mr Sponge’s Sporting Tour 243: I think I heard Mr. Plummey, the butler, say he declined.
1881		Punch 23 July 25/2: The same aged lover was bidding, with rather a ‘plummy’ voice, the More-than-Middle-Aged Heroine ‘good bye for ever’.
1921		B. Pain Marge Askinforit 40: [He] was perhaps the most perfect butler that the world has yet seen; his magnificent presence, plummy voice, exquisite tact, and wide knowledge made him beyond price.
1937		H. Walpole John Cornelius 150: His rather rich plummy voice, the voice of a man who is accustomed to reading prayers in church.
1944		L.A.G. Strong All Fall Down 90: You get that artificial, pumped-up manner with lots of 'em when they're not sure of themselves. Plummy voice, false emphasis, heartiness, and so on.
1953		P. Larkin letter 3 Apr. in Thwaite Sel. Letters (1992) 195: Plummy, fruity dead-fish voice.
1959		K. Waterhouse Billy Liar (1962) 108: She was talking to him in her comfortable plummy voice.
1977		(con. 1941) R. Beilby Gunner 50: The plummy British accent of the arch defector, Lord Hawhaw.
1978		L. Kramer Faggots 72: The rabbi, Earl Chesterfield, Oxford-educated, plummy-toned.
1985		B. Humphries Traveller’s Tool 75: Pronounced Coh-burns, I’m told by some plummy-voiced Pom.
1999		Indep. Mag. 29 May 3: You need to be a terrific snob and have a plummy voice.
2000		N. Griffiths Grits 275: Ther’s been a glut uv such programmes recently [...] invariably hosted by some plummy-voiced prick.
2003		Guardian 2 July 🌐 Certainly, he plays the English eccentric better than most, with his gorgeously plummy voice.
2023		R. Milward Man-Eating Typewriter 350: [T]he New Radical Left [...] plummy self-righteous squares with beards and duffel coats.

4. (Scot.) dull.

1935

(con. 1920s) McArthur & Long No Mean City 53: ‘Sit still, Ella!’ he commanded, ‘and don’t be plummy (dull).’.