milky bar kid, n. — Green’s Dictionary of Slang

milky bar kid n.

[the child advertising the Milky Bar, a sweet, was known as the Milky Bar Kid]

1. (Aus. prison) a petty criminal.

1990

Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Milky bar kid. One who burglarises local stores. Has contemptuous overtones reserved for small time criminality.

2. (N.Z. prison, also milkweed) a skinhead.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 116/2: milky bar (also milky bar kid) n. a skinhead [...] milkweed n. a skinhead.