Green’s Dictionary of Slang

(Aus.) to run, unexpectedly and to the bookmakers’ advantage, contrary to expectations and odds.

1968		J. Alard He Who Shoots Last 86: ‘She’s blown in the bettin’,’ said a suspicious Ragged. ‘Looks like we’re on da wrong tram,’ agreed the Wrecker.
2010		Sydney Morn. Herald 4 Apr. n.p.: ‘I have been watching with great interest recently the number of fancied horses that blow in the betting and race like dromedaries’.