Green’s Dictionary of Slang

(Aus./N.Z.) an extremely lucky person.

1897		W.T. Goodge ‘Great Aus. Slanguage’ in Baker Aus. Lang. (1945) 117: And a tin-back is a party / Who’s remarkable for luck.
1912		Sport (Adelaide) 24 Aug. 14/1: They Say [...] That Galloper B. the tinny, out-pointed J.T. [...] with the king hit.
1955		D. Niland Shiralee 142: Tin-bum, they call me. I get on to opal [...] wherever I sink a shaft.
1968		G. Slatter Pagan Game (1969) 158: He’s been a bit of a tin-bum [...] Not like me. I’m always shit out of luck.
1975		Les Ryan Shearers 79: Good on yer, Joe. You alays were a tin-arse [GAW4].
1982		H. Beaton Outside In I i: Tin arse!
1988		McGill Dict. of Kiwi Sl. 113/1: tin arse lucky person; also tinbum.
2001		Age (Melbourne) 10 June 🌐 Trainer Colin Alderson said after De Gaulle Lane’s win: ‘Andrew is just a tin arse when it comes to picking these horses.’.