Green’s Dictionary of Slang

(N.Z. prison) to put on a balaclava prior to committing various forms of crime.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 13/1: ballie up to put on a balaclava with criminal intent, in order to perform a burglary, robbery, daylight murder, rape, or any other crime that requires the wearing of a balaclava to ensure the perpetrator’s anonymity:.