Green’s Dictionary of Slang

onk n.1

[pron.]

(Aus.) a franc.

[Aus]Aussie (France) VII Sept. 15/2: We were too amazed to speak when he handed over the onks, so tried to restore our voices with the great cure-all.
[Aus]Aussie (France) XII Mar. 1/2: We will only sting you Un ’Onk for the Lot.