Old English læwede "nonclerical," of uncertain origin but probably ultimately from Vulgar Latin *laigo-, from Latin laicus (see lay (adj.)). Sense of "unlettered, uneducated" (early 13c.) descended to "coarse, vile, lustful" by late 14c. Related: Lewdly; lewdness.[lewd etymology, lewd origin, 英语词源]