Green’s Dictionary of Slang

an eccentric person.

1856		Punch XXXI 201: ‘What’s a cure?’ The mud was thick, the crossing clean – A well-dressed man, genteel of mien – Walked through the first (he might be poor) – The sweeper muttered ‘He’s a cure’.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1866		Wild Boys of London I 106/2: ‘I don’t want to make no row,’ said Jack. ‘Sam must be a cure if he thinks I does.’.
1874		J. Greenwood Wilds of London (1881) 95: And all at once to me she cried, / You are a perfect cure!
1888–94		‘Walter’ My Secret Life (1966) V 941: All this usually amused them, but occasionally they objected angrily, — ‘You are a cure’ (a cant phrase then).
1892		‘F. Anstey’ Voces Populi 319: They are cures, those blackies.
1898–1900		H. Lawson ‘Brighten’s Sister-in-Law’ in Roderick (1972) 559: Jim was turning three then, and he was a cure.
1923		‘Bartimeus’ ‘In the Dog-Watches’ in Seaways 20: Didn’t I say she [i.e. a monkey] was a cure?
1938		F. Anthony ‘Rivals’ in Me And Gus (1977) 64: Isn’t he a cure?
1971		(con. WWII) B. Aldiss Soldier Erect 112: A mucker of mine down in M/T [...] He’s a real cure.