Green’s Dictionary of Slang

(N.Z. prison) a reliable, loyal, trustworthy individual, who is staunch, a prized prison quality.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 177/2: staunch adj. 1 reliable, true, solid, honest, faithful 2 brave, tough, resilient. 3 clever, commendable. 4 violent, threatening [...] staunchie n. an inmate who is staunch.