K | 37 | A Dictionary of the Underworld | Eric Partridge

ABSTRACT

kangaroo, n.—5. (Often shortened to kanga or kangar.) A prison warder: convicts'. English since ca. 1925, Aus. since ca. 1930. Jim Phelan, Jail Journey, 1940 (kangar); B., 1953 (kangaroo and kanga). Rhyming on synonymous screw.