obsolete except in lukewarm (late 14c.), from Middle English leuk "tepid" (c. 1200), a word of uncertain origin, perhaps from an unrecorded Old English *hleoc (cognate with Middle Dutch or Old Frisian leuk "tepid, weak"), an unexplained variant of hleowe (adv.) "warm," from Proto-Germanic *khlewaz (see lee). Old English also had wlæc "tepid, lukewarm," which survived in Middle English as wlake. In Middle English lew-warm was a parallel form to luke-warm. Related: Lukely; lukeness. Other now-obsolete formations were luke-hot (late 14c.), luke-hearted (c. 1500).