Green’s Dictionary of Slang

1. (also headings) usu. as head ’em: to play ‘two-up’ [cite 1902 suggests any form of gambling].

1886		Eve. News (Sydney) 22 May 3/6: We went down into the hollow, and we had a very fair game. Some of us ‘headed ‘em.’ some went at pitch-and-toss, and two lots went for ‘nap’ [...] Anyhow, we enjoys our Sunday, and I can’t see no more harm in playing headings [...] on Sunday.
1889		Dead Bird (Sydney) 9 Nov. 6/2: No sooner are the crowd set down [...] than a ‘two up’ or ‘heading ’em’ school starts.
1891		Dead Bird (Sydney) 17 Jan. 1/2: Taught Juno to ‘head ’em’ and Doto to dance.
1902		‘Dads Wayback’ in Sun. Times (Sydney) 16 Nov. 5/5: ‘[T]hey jines er gaffin’ school an’ heads ’em, or plays two up an’ ther like o’ that’.
1905		Argyle Liberal (NSW) 7 Nov. 2/4: I approached him while Bob went in the direction of Ready, who was engaged ’eaden ’em with one of the young R—’s.
1915		C.J. Dennis ‘A Spring Song’ in Songs of a Sentimental Bloke 15: Jist ’eadin’ ’em, an’ doin’ in me gilt.
1920		Truth (Brisbane) 11 Jan. 11/6: [headline] IS TWO-UP TWO-UP WHEN IT’S CALLED HEADING ’EM?

2. (Aus.) to toss up for.

1889

Dead Bird (Sydney) 24 Aug. 7/2: He headed the boys for the bundle and came out half a caser a head.

3. to throw ‘heads’ in a game of two-up.

1949		L. Glassop Lucky Palmer 100: And he’s — headed ’em!
1966		J. Holledge Great Aust. Gamble 100: The spinner bets that he will ‘head ’em’, and naturally the others are backing tails [ibid.] 101: They hit the ground, and from every throat (if they are the same) comes the cry: ‘He’s headed ‘em,’ or ‘He’s tailed ’em’.