Green’s Dictionary of Slang

a negative intensifier, a euph. for damned adj.

1845		R.S. Surtees Hillingdon Hall III 274: All the true and undeniable tramps [...] rose to a man, and swore we'd be blank’d if he should.
1866		Dundee Advertiser 8 Nov. 3/3: When they howled being spanked, / She just said, ‘You be blanked,’ And calmly continued to rap ’em.
1885		Bulletin (Sydney) 13 June 20/1: Arouse! Let pallid nations know, / And, knowing, let them quake, / You’ve gone into the butcher-trade, / No dashed-and-blanked mistake.
1888		J. Runciman Chequers 19: Damn it, gal! – do you mean to say you’ve deceived your father so you might git out along of a blanked lunatic?
1894		Shields Dly Gaz. 26 Apr. 3/3: ‘Now look ’ere, you blanked Irish scum, you’re to clear out o’ this.’ [...] ‘Now don’t let a single blanked one of them through’ [...] said the Captain.
1898		(con. 1875) F.T. Bullen Cruise of the ‘Cachalot’ 43: Moreover, we were informed that he ‘wouldn’t have no adjective skulking’ [...] after wasting the ship’s time and property in such a blanked manner.
1901		A. Binstead More Gal’s Gossip 42: She sobbed something about being dash-blanked if she wouldn’t almost sooner have been charged with simple desertion.
1906		C. M’Govern Sarjint Larry an’ Frinds 26: Oi was too blanked surprised to do nothing except what dey told me to.
1910		Wodehouse Psmith in the City (1993) 52: A somewhat dashed, blanked idiot. [Ibid.] 135: What the dickens are you standing there for, mooing like a blanked cow?
1917		‘Banjo’ Paterson ‘His Masterpiece’ in Three Elephant Power 123: ‘Acres be d——d!’ Billy would scornfully reply; [...] ‘D’ye think we were blanked cockatoo selectors!’.
1934		T. Wood Cobbers 41: Who’s been handing you out stuff about slings? Slings be blanked.