Jephthah's origins are a sign of moral decay in Israel, especially in the area of sexuality, marriage, and family. This is related to religious decay, because unfaithfulness toward the Lord (whore after,
Judges 8:33) leads to unfaithfulness in human relationships.
1 Now Jephthah the Gileadite was a mighty warrior, but he was the son of a prostitute. Gilead was the father of Jephthah.