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), or from the Middle Dutch or Old Frisian words.
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).
masc. proper name, from Latin Lucas (Greek Loukas), contraction of Lucanus literally "of Lucania," district in Lower Italy, home of the Lucani, a branch of the Sabelline race. St. Luke, the Evangelist, is believed by some scholars to have been a Greek or Hellenized Jewish physician of Antioch. His feast day (Oct. 18) was formerly Lukesmas.