Green’s Dictionary of Slang

1. (US) a prostitute.

1856		Life in Boston & N.Y. (Boston, MA) 25 Oct. n.p.: Ned K—n swears he will not go after negro snaps any more.
1856		Life in Boston & N.Y. (Boston, MA) 22 Nov. n.p.: Mary S—n, one of the most notorious private snaps in this city.
1856		Life in Boston & N.Y. (Boston, MA) 22 Nov. n.p.: The are the greatest ‘snap rangers’ in the Fourth District. You can see them at every Dutch ball [...] drinking r.g.

2. a womaniser, a philanderer.

1856

Life in Boston & N.Y. (Boston, MA) 22 Nov. n.p.: That dirty rat and nigger snap ranger, Ben H — , the fancy lawyer. The time you go visiting your black beauty, look out, or you will get caught in bed with her again.