Fishmonger

The term "fishmonger" has a double meaning here. Of course it means one who sells fish, a rather low class profession at the time. "Fishmonger" was also a sort of euphemism for a "pimp". In this case Hamlet accuses Polonius of selling his daughter off for information about Hamlet. Recall, Polonius planted Ophelia to "bump" into Hamlet while they listened in hiding.