Green’s Dictionary of Slang

(Aus.) venereal disease.

1932		(con. 1910s) J.T. Farrell Young Lonigan in Studs Lonigan (1936) 146: ‘You better go to a doctor,’ said Studs. ‘I ain’t got the jack,’ said Paulie.
1944		in T. Hartley gloss. in Simes DAUS (1993).
1950, 1955		‘No. 35’ Argot in G. Simes DAUS (1993).
1960		J. Iggulden Storms of Summer 297: Some rotten poxy bitch of a chromo dobbed them in . . . They reckon she was rotten with the jack so they never paid her.
1965		L. Haylen Big Red 21: Kept a cat house she did. The hottest in town. [...] You could get the ‘Jack’ there too if you weren’t careful.
1973		(con. 1940s–60s) Hogbotel & ffuckes ‘Pull me Dungarees Down’ in Snatches and Lays 54: You’ve gone and given me the jack, Mac.
1985		R.G. Barrett You Wouldn’t Be Dead for Quids (1989) 88: You’ve probably been stuffed by half the Astra Hotel and I’ll end up with the jack.
1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Jack. 2. Venereal disease. As in ‘the jack’, ie usually syphillis.