fleur-de-lis (n.)

also fleur-de-lys, mid-14c., from Anglo-French flour de lis "lily-flower" (see lily), from Old French, literally "flower of the iris," especially borne as a heraldic device on the royal arms of France. There is much dispute over what it is meant to resemble; perhaps an iris flower, or the head of a scepter, or a weapon of some sort. In Middle English often taken as flour delice "flower of joy, lovely flower" (hence Anglo-Latin flos deliciae); also flour de luce "flower of light" (as if from Latin lucem).