Green’s Dictionary of Slang

(W.I., orig. Und.) a cheat, a hypocrite, anyone unethical.

1961		Cassidy Jamaica Talk 217: Another [word] means specifically ‘an alias-man’ (sometimes merely an alias) and more generally a coarse, rough-spoken person.
1977		D. Powis Signs of Crime 172: Alias man A criminal, especially a morally worthless cheat or hypocrite (West Indian term, originally an eighteenth century English expression).
1989		J. Morton Lowspeak 12: Alias man – criminal, worthless person generally.