Green’s Dictionary of Slang

(orig. US) a prostitute who works either lit. in cabs and trains or poss. from or at a brothel.

1859		Matsell Vocabulum.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1895		Crowe Aus. Sl. Dict. 14: Cab Moll, a low woman.
1942		Berrey & Van den Bark Amer. Thes. Sl.
1949		Monteleone Criminal Sl. (rev. edn).
1960		(con. 1950-1960) R.A. Freeman Dict. Inmate Sl. (Walla Walla, WA) 22: Cab-moll – a female crook who lures her marks into taxicabs for clipping.
1999		(ref. to late 19C–1900s) G. Seal Lingo 45: A cab and drum were terms for a brothel – cab molls, or just molls were those who worked in them.