A lot vs. Alot: 9 Grammatical Pitfalls
1620s, a cry to call attention from a distance, a variant of who. As a command to stop a horse, it is attested from 1843, a variant of ho. As an expression of delight or surprise (1980s) it has gradually superseded wow, which was very popular 1960s.
A pickpocket; whiz (1925+ Underworld)