Green’s Dictionary of Slang

peaky adj.

sickly-looking, by ext. weak, feeble.

1853		implied in peakyish
1873		‘Cuthbert Bede’ Little Mr. Bouncer 19: You pretend to be Æger, or sick and peaky, when you’re in robust health.
1873		Sl. Dict.
1881		Manchester Courier 25 June 5: A Texas Mother-In-Law [addressing a policeman] To think of this peaky, little, worthless, spindle-shanked, goggled-eyed whelp getting clear off.
1915		M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 215: peaky, peeky, sickly. ‘She is looking peaky from a cold but otherwise well.’.
1916		W. Pett Ridge Madame Prince 32: One of ’em looks a bit peaky.
1930		K.S. Prichard Haxby’s Circus 154: Mart decided Max was looking a bit peaky: the child really needed a change.
1947		D. Davin For the Rest of Our Lives 194: He remembered how when he was a child if a hen got sick – peaky his mother used to call it – she slunk aside from the rest.
1958		D. Stivens Scholarly Mouse and other Tales 46: Look a bit peaky, both of you. I’ll take you in hand. Long bouncy walks for both of you will be the cure.
1960		H.E. Bates When the Green Woods Laugh (1985) 287: You look a bit peaky, Mr Jerebohm.
1978		A. Ayckbourn Joking Apart II i: You’ve been very peaky lately. Can’t we have a proper holiday sometime?
1989		T. Blacker Fixx 198: You’re looking a bit peaky these days.
1993		I. Welsh Trainspotting 247: You look a bit peaky. Probably just a touch of this little bug that’s doing the rounds.
2000		T. Blacker Kill Your Darlings 230: You all right? [...] You look a bit peaky.

In derivatives

peakedy (adj.)

weak, ill.

1956

N. Algren Walk on the Wild Side 58: ‘Folks looken a bit peakedy,’ Dove observed.

peakyish (adj.)

ill, ‘under the weather’.

1853		‘Cuthbert Bede’ Adventures of Mr Verdant Green (1982) I 84: He ain’t a very lively picter, is he? [...] peakyish you feel, don’t you.
1873		‘Cuthbert Bede’ Little Mr. Bouncer 13: Hullo, Giglamps [...] You look peakyish. What’s the row?