Louse is a slang term for a contemptible person."Louse up" is slang for "botch" and "spoil." Lousy is slang for "well-supplied" (lousy with money) and "unpleasant," "inferior," "worthless" (a lousy cold, a lousy meal, a lousy show). Lousy also means "infested with lice"; if you wish to impress friends, say pediculous.
Dictionary of problem words and expressions. Harry Shaw. 1975.