Hip and thigh — It seems to be a phrase, to express a desperate attack, attended with the utmost hurry and confusion: and perhaps intimates, that they all fled before him. So he smote them in the hinder parts. Rock Etam — A natural fortress, where he waited to see what steps the Philistines would take.
Related Commentaries of Judges 15:8
Judges 15:8
8 And he smote them hip and thigh with a great slaughter: and he went down and dwelt in the top of the rock Etam.