Green’s Dictionary of Slang

1. (Aus./N.Z.) excellent, first-rate, the best of its type; also ext. to dinky-di-do.

1905		J.W. Carr ‘Words from Northwest Arkansas’ in DN III:i 77: dinky, adj. [...] 2. Right, satisfactory. ‘It’s just all dinky’.
1916		All Abaht It Nov. 10: There’s a melancholy Private / With his chest upon his back, / Who tells the London damsels / He’s a DINKIE DIE ANZAC.
1918		Campbell & Nelson [bk title] The Dinky-Di Soldier and other jingles.
1924		G.H. Lawson Dict. of Aus. Words And Terms 🌐 DINKY-DI — Integrity; reputable.
1924		(con. WWI) A.G. Pretty Gloss. of Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: dinky-die. An oath of truthfullness [sic].
1936		(con. 1830s–60s) ‘Miles Franklin’ All That Swagger 402: Letters fell from the pockets, an inscription uppermost. ‘Darling, dinkydi Brian.’.
1941		N.Y. Herald Trib. 29 June 9/2: A truth may be confirmed in either of two ways: You’ll hear that ‘it’s dinkum’ or sometimes that ‘it’s so, dinkie die’.
1942		Sun 17 Feb. 4/3: Smith, on being sentenced to three months gaol, said: ‘If the Japs come a man might get a fair, dinky go.’.
1940		Mail (Adelaide) 18 Feb. 15/4: My jewellry is not fair dinkum, it’s dinky-die.
1951		Cusack & James Come in Spinner (1960) 388: ‘You ought to have seen me sitting there like Jacky wrapped up in an ermine cape Byron brought back from Yalta!’ ‘Ermine?’ ‘Dinky-di ermine!’.
1960		A. Seymour One Day of the Year I i: I’m a dinky-di Aussie.
1973		(con. 1930s) F. Huelin ‘Keep Moving’ 29: We’re dinky-dy Aussies, born in th’ bloody country.
1973		Australian 19 Sept. 14 n.p.: If one has the ability to drink oneself into an alcoholic stupor without falling flat on one’s face in front of one’s mates, one apparently has then achieved the true blue hallmark of excellence of today’s dinky-di Aussie [GAW4].
1987		(con. 1968) Bunch & Cole Reckoning for Kings (1989) 217: ‘Co Tho, this is Tarpy,’ he introduced. [...] ‘He is dinky-dao.’.
1988		McGill Dict. of Kiwi Sl. 37/1: dinky/dinky-di true; ‘Hadlee better than Lillee? Dinky-di, mate.’.
1996		Penguin Bk of More Aus. Jokes 66: ‘Bullshit.’ ‘No, I’m dinky-di.’.

2. true, honest, genuine; note mis-defined as a n. in cit. 1967.

1941		A. Gurney Bluey & Curley [synd. cartoon] Can’t yer put it in dinky-di Aussie?
1955		N. Pulliam I Travelled a Lonely Land (1957) 232/2: dinky di – true, honest.
1962		(con. WWII) J.O. Killens And Then We Heard The Thunder (1964) 356: ‘I feel much better, thank you.’ [...] ‘Dinky die?’.
1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxiv 4/3: dinki di: The truth, the whole truth and nothing but.
1979		D. Maitland Breaking Out 63: Questioning the prudence of a dinki-di Aussie getting hooked up with a bloody darkie.
1986		R. Beckett Dinkum Aussie Dict. 19: Dinki Di: True blue; on the level. The absolute truth.
1986		C. Bowles G’DAY 91: The fair dinkum, dinki-di, true-blue Australians are mostly found in RSL clubs getting rotten .
2000		Indep. Traveller 15 Jan. 1: A real true-blue, dinky-di, fair dinkum horse-race.
2005		M.B. ‘Chopper’ Read Chopper 4 187: I’m not dirty on the poor old dinki di Abos.
2018		R. O’Neill ‘Ocker’ in The Drover’s Wives (2019) 181: He was a dinky-di Aussie battler, and so was she. Too right.