Haha I had to research that, as i had no idea what you were talking about, (im not australian)
Buckley & Nunn
The origin of the Australian slang term "Buckley's chance" (meaning "little or no possibility" or "no chance at all") has been explained as rhyming slang, viz, "Buckley and Nunn" (meaning "None"); and as a punning reference ("You've two chances: Buckley's and none").[6][7] Australians in states other than Victoria generally believe the idiom derives from the adventures of escaped colonial convict William Buckley
