Origin: 1250–1300; Middle English whelme, apparently blend of dial. whelve (Old English gehwelfan to bend over) and helm2 (v.) (Old English helmian to cover)
c.1300, probably from a parallel form of O.E. -hwielfan (W.Saxon), -hwelfan (Mercian), in ahwelfan "cover over;" probably altered by association with O.E. helmian "to cover" (see helmet).