Shnook undoubtedly derives from the Yiddish "
schnook" meaning an easily victimized person; i.e., "the poor schnook gave his banking information to an internet scammer." But in American usage over the years, "
shnook" has come to mean a person that behaves in a mischievous or naughty way. For example, small children are "
shnooks" when they misbehave. Politicians are "shnooks" when they get involved in scandals.