Green’s Dictionary of Slang

1. in the game of two-up, the person who takes charge of the apparatus and of the money staked by the main bettors.

1911		L. Stone Jonah 217: The boxer had to offer twelve to ten to cover Chook’s stake.
1966		J. Holledge Great Aust. Gamble 100: Each school is controlled by at least one ring-keeper or ‘boxer’.

2. a commission paid to that person.

1910		Worker (Wagga, NSW) 25 May 3/5: ‘How is it, you tail backers, fer a little bit towards the gas?’ Tail backers generally responded with a shower of silver as a ‘boxer’.
1933		(con. WWI) A.E. Strong in Partridge Sl. Today and Yesterday 287: Of course I had to give the ring-keeper a boxer.
1938		Press (Canterbury) 2 Apr. 18: A ‘boxer’ is a gratuity to the ‘ringie’ at two-up.
1949		L. Glassop Lucky Palmer 168: The man running a two-up game takes a percentage of the winnings of the spinner when there is a run of heads, but when tails are falling he depends on contributions from the tail backers. In response to the fat man’s appeal for a ‘boxer,’ a few florins and shillings were tossed into the ring.