Green’s Dictionary of Slang

1. insane, eccentric; ext. as balmy in/on the crumpet.

1851		R.S. Surtees Young Tom Hall (1926) 222: Captain Balmeybucke, who worshipped her eyes, and worshipped her nose, and worshipped her lips, and worshipped her teeth [...] and worshipped everything about here.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 217/2: I give below a vocabulary of their talk to each other: [...] Balmy .... Insane.
1870		Hotten Sl. Dict.
1879		‘Autobiog. of a Thief’ in Macmillan’s Mag. (London) XL 506: Then I carried on a nice game, what with the trips and the drink I very near went balmy (mad).
1886		Sporting Times 15 May 1/1: You see, marm, that your okeblo is a bit balmy in the crumpet.
1887		J.W. Horsley Jottings from Jail 98: I tried to act the balmy (i.e., sham mad).
1892–3		H. Lawson ‘Two Boys at Grinder Bros’ in Roderick (1972) 27: Arvie’s getting balmier than ever. [...] Here comes Balmy Arvie.
1894		Huddersfield Chron. 23 Oct. 4/2: John Abraham [...] admitted to the Magistrates at Westmintser, that he was called ‘balmy on the crumpet’.
1896		A. Morrison Child of the Jago (1982) 96: Old Beveridge had eccentric talk and manners, and the Jago regarded him as a trifle ‘balmy’.
1900		Marvel 22 May 15: Round and round they went like balmy blokes.
1901		Bateman & LeBrunn [perf. Kate Carney] Liza Johnson 🎵 Sings about his ‘Rosey Posey’; he’s gone balmy on the tune.
1902		Eve. Teleg. (Dundee) 25 Nov. 3/3: Innumerable and curious euphemisms for ‘mad’ [...] ‘balmy in the crumpet’, [...] ‘a tile loose,’ ‘soft in the cocoa-nut,’ ‘off his rocker,’ ‘off his nut,’ ‘off his chump’ [and] ‘a little bit off the top’.
1904		Sun. Times (Perth) 7 Feb. 4/5: The assaults of some piano fiend would nearly send him balmy.
1908		Vanguard Library 31 Mar. 12: Whoever he was he must have been a bit balmy on the crumpet.
1911		L. Stone Jonah 38: At regular intervals Chook ‘went balmy’ over some girl or other.
1915		P. Macgill Amateur Army 112: We are a balmy regiment.
1919		C. Hamilton William – An Englishman (1999) 72: You are balmy on the crumpet, both of you. Balmy.
1922		Joyce Ulysses 307: Do you know that he’s balmy? Look at his head. Do you know that some mornings he has to get his hat on with a shoehorn. [Ibid.] 724: Didnt he look a balmy ballocks.
1926		Dundee Eve. Teleg. 19 Feb. 4/3: A motor car skidded and made its way into a baker’s shop last week. Gone balmy on the crumpet, perhaps.
1930		E. Glyn Flirt and Flapper 98: Flirt: You could start by showing your friends an example of good manners and consideration— Flapper: They’d think I was balmy .
1933		Hecht & Fowler Great Magoo 94: They’re going balmy.
1937		A. Christie Murder in the Mews (1954) 115: People do shoot themselves when they’re a bit balmy.
1943		in T. Harrisson Mass-Observation War Factory: Report 6: I don’t like being inside like this; I sometimes feel if I don’t get out I shall go balmy.
1944		Cheltenham Chron. 8 July 4/4: There used to be a well-known Cheltonian who [...] would wax eloquent on the theme that we are a bit balmy on the crumpet.
1948		C. Day Lewis Otterbury Incident 66: In fact he’s balmy. But quite harmless.
1957		R. Prather Always Leave ’Em Dying 53: This one’s really gone, ain’t he? If this ain’t the craziest story I’ve ever heard, then I’m balmy muhself.
1960		B. Kops Dream of Peter Mann Act III: You are a mad crank who’s gone balmy.
1980		R. Dahl Twits (1982) 75: ‘He’s balmy!’ ‘He’s batty!’.
1989		H. Rawson Dict. of Invective (1991) 342: balmy in the crumpet, bats in the belfry.

2. drunk; tipsy.

1850		Mountain Sentinel (Ebensburg, PA) 4 Apr. 1/4: They may have somebody, as a married man once said, to ‘pull off their boots when they get a little balmy’.
1875		Cambria Freeman (Edensburg, PA) 22 Oct. 1/7: The word Drunk is incomparably richer in synonyms than any other word [...] to this we may add: steaming it, goggle-eyed, have a brick in his hat, balmy, o be joyful.
1886		Sporting Times 3 Apr. 7/5: I’m sometimes a guest at the banquet, / And get balmy on make-believe booze.
1895		Herald (Melbourne) 27 Aug. 2/7: Well, one day, in Tasmania, Mushroom Billy and his pal, who were very great friends, went into the township and got balmy (influenced by drink).
1904		Belfast News-Letter 15 June 6: ‘Balmy,’ [...] ‘sewn up’ [...] and others of the same kidney are all of nineteenth century invention.