late 15c., according to The Middle English Compendium a variant of Middle English licius "delicious" (c. 1400), which is a shortening of delicious, with the variant form perhaps influenced by Old French luxure, lusure. But OED 2nd ed. and Century Dictionary are against all this and the former considers it "of obscure origin" while the latter suggests lusty with a pseudo-Latin ending. John Palsgrave, the 16c. grammarian, spelled it lussyouse. Related: Lusciously; lusciousness.