Green’s Dictionary of Slang

very sick; also fig. use.

1680		Merry Maid of Islington 9: O my stomach’s sick as a Cat.
1867		R. Broughton Cometh up as a Flower 301: He was sick as a cat, I dare say, crossing; he’s an awful bad sailor.
1872		Schele De Vere Americanisms 597: Sick as a dog is [...] replaced by sick as a cat, while to ‘vomit as a cat’ is said to have as little reference to the animal as dog-cheap has (Latham, English Language), but to mean throwing up like a cataract, whch, if true, would be quite American in its proportions.
1883		Inter Ocean (Chicago) 13 Feb. 6/5: Denver has been sick for a week — sick as a lame cat in a deserted garage.
1893		W.S. Walsh Literary Curiosities 140: Cat, As sick as a, [...] It seems that the original ran: As sick as cats With eating rats.
1936		Auden & Isherwood Ascent of F6 II iv: Ian would be feeling sick as a cat.
1938		H. Drake-Brockman Men Without Wives I i: I bet friend Lovatt’s sick as a cat because he’s not safely out on the run, avoiding this little party.

very hungry, thus not sick at all.

1738

Swift Polite Conversation 32: Poor Miss, she’s sick as a Cushion, she wants nothing but stuffing.

very sick; also fig. use.

1599		H. Buttes Dyets Dry Dinner n.p.: He that saieth he is dog sick, or sick as a dog, meaneth doubtless, a sick dog.
1667		R. L’Estrange (trans.) Visions of Quevedo 303: I am as sick as a Dog of Powdering, Curling, and playing the Lady-bird.
1705		Vanbrugh Confederacy II i: He’d make me sick as a dog.
1776		G. Colman Spleen II i: I was sick as a dog immediately after dinner yesterday.
1833		M. Scott Tom Cringle’s Log (1862) 361: I [...] can’t stand that—sick as a dog.
1836		T. Haliburton Clockmaker I 106: We’ve had politics with us, till we’re dog sick of ’em.
1837		R. Barham ‘The Bagman’s Dog’ Ingoldsby Legends (1840) 321: Poor Anthony Blogg / Is as sick as a dog.
1849		E. Gaskell Mary Barton I 35: Folks is as sick as dogs all the time they’re at sea.
1856		C. Reade It Is Never Too Late to Mend II 39: The first crucifixion Eden saw he turned as sick as a dog.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor (1968) III 279/2: Very bad drink it is – the worst – it makes me sick as a dog.
1874		J.B. Stephens ‘The Headless Trooper’ Poems 104: The ’possums all within a mile / Went home as sick as dogs.
1884		Henley & Stevenson Admiral Guinea III ii: I’m dog-sick of Jack Gaunt.
1884		C.F. Lummis letter 25 Nov. in Byrkit Letters from the Southwest (1989) 111: Oh, God, but I’m sick as a dog!
1905		G.W. Peck Peck’s Bad Boy Abroad 68: A man far away from home, sick as a dog, with no loving wife to look after him.
1909		J.W. Carr in ‘Word-List From Northwest Arkansas’ in DN III:v 403: sick as a dog, adj. phr. Very sick. ‘I ate something last night that didn’t agree with me and I was sick as a dog for awhile.’.
1917		Conneautville Courier (PA) 4 July 8/3: This homely phrase ‘Sick as a Dog’ indicates that the sickness of dogs must be the worst kind of all sicknesses.
1923		H.C. Witwer Fighting Blood 23: She insists on me taking a swallow of cod liver oil [...] and it makes me as sick as a dog.
1933		E.A. Robertson Ordinary Families 43: All my troupe were sick as dogs.
1935		(con. 1920s) J.T. Farrell Judgement Day in Studs Lonigan (1936) 552: I got dizzy and sick as a dog.
1947		J. Maclaren-Ross Of Love and Hunger 197: Later on I was sick as a dog.
1950		Courier-Jrnl (Louisville, KY) 18 Sept. n.p.: Which is the worst to be: ‘As sick as a pup.’ ‘As sick as a horse.’ ‘As sick as a mule’.
1957		D. Niland Call Me When the Cross Turns Over (1958) 12: I’m sick, Snow, sick as a bloody dog.
1966		C. Wood Fill the Stage With Happy Hours (1967) Act I: I’ve been sick as a dog.
1971		Chillicothe Gaz. (OH) 27 Mar. 23/1: ‘Don’t ever say I’m “cured” [...] becaue if I took just one drink today, I’d be right back where I was, sick as a dog’.
1980		A. Fugard Tsotsi 14: Ja. Sick man. Like a dog. Sick like a dog.
1992		S.L. Hills Tragic Magic 2: I was sick as a dog but I had to go out.
2000		Guardian G2 22 Feb. 11: I went for the morning-after pill and felt sick as a dog.
2004		(con. 1980s) N. ‘Razor’ Smith A Few Kind Words and a Loaded Gun 287: The judge agreed [...] The police were as sick as dogs.

extremely ill.

1759–67		Sterne Tristram Shandy (1949) 456: I am as sick as a horse, quoth I.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn) n.p.: Sick as a Horse. Horses are said to be extremely sick at their stomachs, from being unable to relieve themselves by vomiting. Bracken, indeed, in his Farriery, gives an instance of that evacuation being procured, but by a means which he says would make the Devil vomit. Such as may have occasion to administer an emetic either to the animal or the fiend, may consult his book for the recipe.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1848		Bartlett Dict. Americanisms 303: sick as a horse. ‘I’m as sick as a horse,’ is a vulgar phrase which is used when a person is exceedingly sick. As a horse is larger than a man, it is customary to use it by way of comparison to denote largeness or excess either in a serious or ludicrous way, as horse-chestnut, horse-leech, horse-laugh, &c.
1848		J.R. Lowell Biglow Papers (1880) 115: It kin’ o’ makes me sick ’z / A horse, to think o’ what he was in eighteen thirty-six.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1907		J.W. Carr ‘Word-List from Hampstead, N.H.’ in DN III iii 199: sick as a horse, adj. phr. Very sick. ‘I was sick as a horse last night.’.
1909		J.W. Carr in ‘Word-List From Northwest Arkansas’ in DN III:v 405: sick as a mule, adj. phr. Very sick.
1931		D.M. Garrison ‘Oilfield Idyls’ in Botkin Folk-Say 150: Just as sick as a mule.
1935		J. Conroy World to Win 58: Honest to God, I’m sick as a horse.
1950		Courier-Jrnl (Louisville, KY) 18 Sept. n.p.: Which is the worst to be: ‘As sick as a pup.’ ‘As sick as a horse.’ ‘As sick as a mule’.

extremely depressed, usu. mentally rather than physically distressed.

1976		Guardian 8 Mar. 16/2: If only [...] Bradford City’s manager had declared himself ’as sick as a parrot’.
1987		Guardian 17 Jan. 18/6: A post-match TV interview with a player [...] included the phrase[s] [...] ‘Sick as a parrot’.
1999		Guardian Editor 17 Sept. 15: Sick as a parrot: [...] of a player disappointed by his/her performance or that of the team.
1999		Indep. Rev. 12 Oct. 8: His opponent can’t believe it: ‘I’m as sick as a parrot, I had no sex, stayed off the beer and did all my limbering-up exercises.’.
2005		Decocrat & Chron. (Rochester, NY) 14 Dec. 27/1: The British Embassy has laucnhed a website to aid English fans [...] translations of phrases like [...] ‘He was sick as a parrot,’ and [...] ‘he puked his guts up’.

very sick.

1890–1904		Farmer & Henley Sl. and Its Analogues.
1900		Columbus Dly Advocate (KS) 7 Apr. 4/6: Didn’t know ‘where they were at!’ / Made them sick as a poisoned rat!
1921		Hartford Republican (KY) 13 May 4/3: Fluke came home from his fishing trip as sick as a poisoned rat.
1937		P. Cheyney Dames Don’t Care (1960) 118: Then Paulette discovers that Benito is sick as a rat.
1979		Sthn Illinoisan (Carbondale, IL) 20 May 3/6: ‘I was sick as a rat [...] My mouth was all blistered and my throat was killing me’.

very depressed or upset.

1928		Graphic (London) 17 Nov. 8/2: Don’t mind what the old boy says [...] They’ve just sat on his leave, and he’s sick as mud.
1934		Wodehouse Right Ho, Jeeves 127: Hearing him attacked, my Cousin Angela’s womanly heart will be as sick as mud.
1938		Dundee Eve. Teleg. 23 Nov. 9/2: ‘She’d be sick as mud if they did leave it alone. She mops up the publicity’.