haunch n.

early 13c., from Old French hanche "hip, thigh; haunch" (12c.), from Frankish *hanka or a similar Germanic source (cognates: Old High German hinkan "to limp," ancha "leg," literally "joint;" Middle Dutch hanke "haunch"). "It is only since the 18th c. that the spelling haunch has displaced hanch" [OED]. Related: Haunches.