Judges 11:3

Then Jephthah fled from his brethren, and dwelt in the land of Tob: and there were gathered vain men to Jephthah, and went out with him.

Jephthah ... dwelt in the land of Tob - on the north of Gilead, beyond the frontier of the Hebrew territories (2 Samuel 10:6; 2 Samuel 10:8).

There were gathered vain men to Jephthah - idle, daring, or desperate; probably the Arabs of the adjoining desert.

And went out with him - followed him as a military chief, They led a freebooting life, sustaining themselves by frequent incursions on the Ammonites and other neighbouring people, in the Style of Robin Hood, or Highland reivers in the border forays, even when England and Scotland were at peace. The same kind of life is led by many an Arab or Tartar still, who, as the leader of a band, acquires fame by his stirring or gallant adventures; and it is not deemed dishonourable when the expeditions are directed against those out of his own tribe or nation. Jephthah's mode of life was similar to that of David when driven from the court of Saul.