Green’s Dictionary of Slang

1. (also get to it) a general excl. of encouragement; in full go it you cripples, crutches / wooden legs are cheap!

1801		G. Hangar Life, Adventures and Opinions II 81: [To] denote a good education, and shew that you have kept good company, be mindfull of the following, which you will apply as the conversation will admit you [...] ‘That’s the barber,’ ‘Go it,’ ‘The tippy and the twaddle,’ ‘What a swell’ .
1815		D. Roberts Sequel to The Military Adventures of Johnny Newcome I 116: Give us a song, my boy! a good one — go it!
1820		‘Peter Corcoran’ ‘Sonnet’ in Fancy 93: The noise of ‘Go it Jack,’ – the stop – the blow.
1821		Egan Life in London (1869) 235: Logic whispered in his ear to ‘go it!’.
1831		‘Gallery of 140 Comicalities’ Bell’s Life in London 24 June 1/2: Go it, Molly! rub his life time out!
1834		Westmeath Jrnl 5 Feb. 4/4: What do you deem the most classical expression of modern times A. Lord Holland’s to the Cabinet—‘Go it, you cripples; crutches are cheap’.
1836		Australian (Sydney) 8 Apr. 4/2: The slang fellows about London cry, ‘go it ye cripple’.
1841		Punch 31 July I 28: Go it, ye cripples!
1842		Whip & Satirist of NY & Brooklyn (NY) 16 Apr. n.p.: Go it you cripple.
1842		Whip & Satirist of NY & Brooklyn (NY) 16 July n.p.: It was go it Dick, go it Devil, go it Gash, go it Fib [...] till they were parted by the bystanders.
1842		Whip & Satirist of NY & Brooklyn (NY) 17 Dec. n.p.: Go it, ye cripples, wooden legs are cheap.
1844		Leeds Times 22 June 6/2: Another victory! Go it, lads!
1845		Cadiz Sentinel (OH) 10 Dec. 3/6: Ourself [...] have beaten nearly half a dozen in each of the other offices, including men, women, boys, devils and baboons! Go it, ye cripples!
1848		‘Ned Buntline’ Mysteries and Miseries of N.Y. II 98: Go it Gus!
1848		‘Epistle from Joe Muggins’s Dog’ in Era (London) 2 Jan. 3/4: All the lame ducks and waddlers are in commotion, and though the right ’uns cry, ‘Go it, yer cripples!’" they don’t fancy being driven afore the committee.
1853		T. Haliburton Sam Slick’s Wise Saws I 294: Go it, my little widder, while you are young.
1857		Life in Boston & N.Y. (Boston, MA) 11 Apr. n.p.: [headline] ‘Go it, ye Cripples’.
1858		A. Mayhew Paved with Gold 157: Didn’t you hear him saying, ‘Go it, you cripple?’.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 149: GO IT, a term of encouragement, implying ‘keep it up!’ [...] or ‘go it, ye cripples, crutches are cheap.’.
1861		T. Hughes Tom Brown at Oxford (1880) 122: Go it, little ’un; serve him out.
1865		Dickens Our Mutual Friend (1994) 805: ‘Go it!’ cried Mr. Sampson [...] ‘Oh yes! Go it, Miss Lavinia Wilfer!’.
1865		R.S. Surtees Facey Romford’s Hounds 334: Go it, ye cripples! Newgate’s on fire!
1873		General Custer letter 10 Sept. in Custer Boots And Saddles (1999) 295: As one by one I dispose of each goodly-sized fragment of a huge onion, I remark, sotto voce, ‘Go it, old fellow! Make the most of your liberties!’.
1874		‘Old Calabar’ Won in a Canter III 12: ‘Go it, ye cripples,’ is shouted on all sides.
1885		Bulletin (Sydney) 8 Aug. 13/4: His Excellency’s opinions were, however, received with much hilarity by the Contingent, and audible observations, such as ‘Go it, old boy!’ and ‘Ain’t his nurse come for him?’ floated amongst the khakee ranks.
1886		Sporting Times 29 May 1/3: ‘Go it, ye cripples! powder’s cheap! / And shot you may buy by the gallon’.
1890–1904		Farmer & Henley Sl. and Its Analogues III 163/2: Go it ye cripples, crutches are cheap (or Newgate’s on fire).
1891		Bird o’ Freedom (Sydney) 21 Mar. 2/2: Go it, you cripples! Any more coming along?
1896		A. Morrison Child of the Jago (1982) 102: Good luck, father [...] go it!
1899		R. Whiteing No. 5 John Street 266: Go it, ye cripples.
1904		Sydney Sportsman (Surry Hills, NSW) 6 July 6/3: [The] shouts of idiotic barrackers who, undertake to not only ‘Go-it-Bob,’ but to issue gratuitous instructions to men trained to the game.
1904		Sydney Sportsman (Surry Hills, NSW) 28 Sept. 6/1: Now, get to it, ye cripples.
1906		E. Pugh Spoilers 133: ‘Go it, ole fat!’ he shouted.
1919		Marvel 3 Mar. 5: Go it Bodder! Good on you! Give it the beast!
1926		K.S. Prichard Working Bullocks 290: Go it, Deb! Stick to it Deb!
1936		W. Holtby South Riding (1988) 434: Go it! Atta boy!
1954		A. Buckeridge According to Jennings (1991) 190: ‘Go it, Jen!’ yelled Darbishire.
1962		K. Waterhouse There is a Happy Land (1964) 23: I shouted: ‘Go it, man!’.
1962		Science Fiction Adventures (no. 26) 61: Good lad. Go it son.
1976		D. Ireland Glass Canoe (1982) 132: Go it, God! [...] Give it to ’em! Stick it right up ’em!

2. as a statement of agreement or acceptance.

1840

Comic Almanack Apr. 223: ‘Go it,’ says I, up to my mettle; ‘Sam Coxe never says no.’.