Is it ensure, insure, or assure?
c.1300, "lascivious, lecherous, unchaste," from Old French luxurios "lustful, lascivious" (Modern French luxurieux), from Latin luxuriosus, from luxuria (see luxury). Meaning "given to luxury, voluptuous" (of persons) is from c.1600. Of things, meaning "characterized by luxury" is attested from c.1650. Related: Luxuriously; luxuriousness.