Old English sceanca "leg, shank, shinbone," from Proto-Germanic *skankon- (cf. Middle Low German schenke, German schenkel "shank, leg"), perhaps literally "that which bends," from PIE root *skeng- "crooked" (cf. Old Norse skakkr "wry, distorted," Greek skazein "to limp"). Specifically, the part of the leg from the knee to the ankle. Shank's mare "one's own legs as a means of transportation" is attested from 1774.