Brewer's: Hip and Thigh
To smite hip and thigh. To slay with great carnage. A Hebrew phrase. (German, Arm and bein.)
Perhaps there may be some reference to the superstition about the ossacrum (q.v.).
“And be smote them hip and thigh with great slaughter.” —Judges xv. 8.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894