Green’s Dictionary of Slang

charlie chap n.

[abbr.; ult. film star Charlie Chaplin (1889–1977)]

(Aus.) a moustache resembling that worn (in character) by Charlie Chaplin.

[Aus](con. WWI) A.G. Pretty Gloss. of Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: charlie chap. A moustache resembling that of the famous film comedian.