Green’s Dictionary of Slang

1. (also gahn! garn! gawn with you! ger on! get on (with you)! get out with you! go on out of that! go on with you!) an excl. used to imply incredulity.

1864		T.F. Upson diary 29 May in Winther With Sherman to the Sea (1958) 112: One said , ‘Jo Johns(t)on has got old Sherman fixed now, and he will soon have to fall back for want of supplies as we have burnt all the bridges as we fell back.’ ‘Gaunnou (go on now),’ said the other, ‘Sherman had duplicates of all those bridges before he started [...] and he can soon replace them’.
1882		E.S. Ellis Huge Hunter in Beadles Half Dime Library XI:271 12/2: Arrah, now, get out wid ye!
1888		J. Runciman Chequers 80: Garn, you farthin’ face! Shet your neck.
1890		Bulletin (Sydney) 23 Aug. 14/3: The bishop said he had [never tasted the beer before]. ‘Go on!’ said the foreman; ‘mean to say you never knock round the pubs. at night?’.
1890		‘F. Anstey’ Voces Populi 88: Ga-arn – yer dotty yerself!
1894		H. Nevinson ‘The St. George of Rochester’ in Keating Working Class Stories of the 1890s (1971) 44: Ger on!
1894		A. Morrison Tales of Mean Streets (1983) 30: ‘Garn,’ said Lizerunt, greatly pleased: ‘le’ go!’.
1896		G.M. Fenn Sappers and Miners 157: ‘I get five-and-twenty shilling a week for working here, not for going to chuck away my life.’ ‘Gahn!’ shouted a man. ‘Your life aren’t worth more nor no one else’s. Who are you?’.
1898		F. Dumont Dumont’s Joke Book 11: Go on! Kiss a girl through the telephone?
1899		C. Rook Hooligan Nights 47: Garn, young Alf, you’re ’fraid.
1905		Pensacola Jrnl (FL) 6 Oct. 6/3: G’wan, youz! He’s drunk.
1906		E. Dyson Fact’ry ’Ands 53: ‘Got off one pound seven ounces since Saterdee,’ she said. ‘Gon! yeh don’t say,’ answered Feathers.
1906		E. Dyson Fact’ry ’Ands 76: ‘Garn,’ he said, ‘no airs. Yer Weary Willie’s brother Sam’.
1907		D. Stewart Shadows of the Night in Illus. Police News 21 Sept. 12/2: ‘Garn, yer bloomin’ idiot [...] I’m Lord Sludge!’.
1908		A.N. Lyons Arthur’s 13: ‘Go on!’ she says.
1910		Bulletin (Sydney) 17 Nov. 11/1: When called upon to make good the loss, cocky said ‘Garn!’.
1914		M. Glass Potash And Perlmutter 41: ‘G’wan!’ he said.
1918		C.J. Dennis ‘A Digger’s Tale’ in Chisholm (1951) 100: ‘Go hon!’ she sez, or words to that effect – / (It’s ’ard to imitate the speech they use).
1919		Aussie (France) 12 Mar. i: The Annoyed Digger: Cripes, — Call that stew? The Ditto Bab: Garn! you wouldn’t growl at that grub in civvie life.
1922		Joyce Ulysses 405: Garn! Have a glint, do.
1922		M.E. Smith Adventures of a Boomer Op. 26: ‘Gwan,’ says I, without even looking up. ‘Nothing doing.’.
1925		S. O’Casey Juno and the Paycock Act II: Gawn with you, child, an’ you only goin’ to be married.
1926		K.S. Prichard Working Bullocks 107: ‘Thought you were dead or something, Red.’ [...] ‘Go on,’ Red replied cheerfully.
1928		(con. WWI) ‘Taffrail’ ‘A Little Drop o’ Leaf’ Little Ship 227: Garn! We ’aven’t ’ad no leaf for months.
1929		J.B. Priestley Good Companions 242: ‘Get on with you!’ said the waitress, who understood this to be some sort of chaff.
1930		N. Lindsay Redheap (1965) 231: ‘Get out,’ said Robert, not displeased at these insinuations. ‘Can’t a man meet a girl by chance without a lot of goats like you getting funny about it?’ .
1932		(con. WWI) L. Mann Flesh in Armour 154: ‘Garn, yer kiddin’, serj’.
1933		J.T. Farrell Gas-House McGinty 204: Gwan, yuh baguh.
1936		(con. 1830s–60s) ‘Miles Franklin’ All That Swagger 126: ‘Go orn!’ said Bella, shrewdly narrowing her eyes and enlarging her suspicions.
1938		J. Curtis They Drive by Night 81: Garn, don’t make me laugh.
1941		K. Tennant Battlers 315: ‘Hundreds of fousands of mines opened, and mills and crushers and all.’ ‘Go on!’ Snow grunted disbelievingly.
1947		N. Streatfeild Grass in Piccadilly 79: Get on, sauce box.
1949		L. Glassop Lucky Palmer 179: ‘OK [...] You great lover, you.’ ‘Lucky’ grinned and said, ‘Garn.’.
1951		Cusack & James Come in Spinner (1960) 137: ‘Say, Guin, why don’t you live in a place with an elevator?’ ‘Garn. This house is a hundred years old.’.
1953		H. Tracy Mind You, I’ve Said Nothing (1961) 79: Ah, g’wan out of that, Missus!
1959		W. Hall Long and the Short and the Tall Act I: evans: Go on, man! bamforth: Straight up. It’s straight up, son.
1965		E. Bond Saved Scene iii: Garn! Yer never seen ’im.
1966		P. White Solid Mandala (1976) 147: ‘Go on!’ said the other, soaring to astonishment.
1970		B. Oakley Salute to the Great McCarthy 187: Garn! Nohoper! Nine-day wonder! Take him off!
1970		C. Brown Down All the Days 75: Ah, g’wan with you!
1981		A. Weller Day of the Dog 1: Garn, brother, ’ave a drink for me.
1983		W. Trevor Fools of Fortune 89: ‘Eerah, get on with you,’ said the girl.
1995		Brendan O’Carroll Chisellers [ebook] Go on outa that, yis pair of fuckin’ drunken wagons .
1996		Penguin Bk of More Aus. Jokes 420: ‘GARN GET FUCKED!’ shouts the contestant.
1997		C. Hiaasen Lucky You 38: ‘Maybe you guys heard — this store had the winning ticket yesterday.’ ‘Go on!’.
1997		C. McPherson The Weir 30: Go on out of that you chancer.

2. (US campus) an excl. of admiration.

1976		Eble Campus Sl. Nov. 3: go on – expression of excited approval, pleasure.
1984		Smiley Culture ‘Cockney Translation’ 🎵 Cockney say Be first, my son! We just say Gwan!