Green’s Dictionary of Slang

(N.Z. prison) used in phr. pertaining to imprisonment.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 191/2: hang the toothbrush n. to stop coming to prison, to retire from one’s career as a criminal [...] take the toothbrush to go to prison. [when a criminal enters the courthouse [...] for a trial, it is common for his friends and/or associated bystanders to call out the expression: ‘Take your toothbrush!’ = ‘Be prepared, you're going to prison’.