Vig?

Whether used by Tony Soprano or your friend with a gambling habit, the term "vig" is everywhere.

Wikipedia offers a good definition. Beyond merely it's Yiddish origin, however, the term is an interesting study in tax incidence. Who "pays" the vig depends on assumptions about the gamblers: whether each gambler has a target amount he is willing to win, a specified amount he is willing to risk, or a tendency to bet more when he believes himself to have an edge.

Wikipedia's vig discussion makes these points very clearly.