Green’s Dictionary of Slang

1. (Aus.) in two-up, the bets laid against the thrower (as opposed to any side bets).

1930		L. Lower Here’s Luck 44: ‘Seven and eightpence. Set the centre! Set the centre!’ ‘Two bob you tail ’em,’ said the milkman.
1966		J. Holledge Great Aust. Gamble 100: The ‘guts’ is sometimes called the ‘centre’.

2. see centre of attraction n.