Albert Barnes Commentary Judges 11:34

"And Jephthah came to Mizpah unto his house; and, behold, his daughter came out to meet him with timbrels and with dances: and she was his only child; besides her he had neither son nor daughter." — Judges 11:34 (ASV)

His daughter came out to meet him - The precise phrase of his vow (Judges 11:31). She was his only child, a term of special endearment (Zechariah 12:10). The same word is used of Isaac (Genesis 22:2, 22:12, 22:16).