"morbid dread of having caught rabies," a psychological condition which sometimes mimicked the actual disease, 1874, Modern Latin, from -phobia + Greek lyssa (Attic lytta) "rabies, canine madness," also the name given to the "worm" of cartilage under a dog's tongue," an abstract word probably literally "wolf-ness" and related to lykos "wolf" (see wolf (n.)); but some see a connection with "light" words, in reference to the glittering eyes of the mad.