Why does Hamlet call Polonius Jephthah?
In the Old Testament (Judges 11 ), Jephthah vows to sacrifice to the Lord the first living thing that comes out of his house if the Lord will give him the victory of the Ammonites. Unfortunately, the first living thing to come out was his own daughter. Thus he was under oath to offer his daughter as a burnt offering.
In the same way, Hamlet is insinuating that Polonius is will to sacrifice his own daughter for personal gain.