Green’s Dictionary of Slang

(Aus.) a prostitute who prefers Aborigine or, during WWII, African-American clients [refers to sexual exploitation of female Aborigines; note Simes (2018) ‘The alleged sense, ‘a coloured, esp. a Negro, pathic’, proposed by Partridge (Dict. Slang (ed.5 1961) [...] whence repeated in uncritically edited dictionaries), is a lexicographer’s phantom and never existed; it arose from Partridge’s misreading of Cusack and James’s prize-winning novel of war-time Sydney].

1946		Smith’s Wkly (Sydney) 2 Nov.1/1: ‘Some of our “Boong Molls”, as we term them in the police force, reserve themselves for the blackmen.’ [ibid.] 1/2: ‘One of the most incorrigible features of the “Boong Moll” business is that many of them are married to Australians and have children.’ [...] ‘After visiting the wharves and making their contacts, the “Boong Molls” take their flashily-dressed and gloating black visitors [i.e. G.I.s] down to the worst haunts of the city.
1951		Cusack & James Come in Spinner (1960) 202: Bloody boong-molls make me sick.