Английский Этимологический словарь - cockatrice

- O.Fr. cocatris, altered by influence of coq from L.L. *calcatrix, from L. calcare "to tread" (calx "heel"), as translation of Gk. ichneumon. A serpent hatched from a cock's egg, it was fabled to kill by its glance and could only be slain by tricking it into seeing its own reflection. Belief in them persisted even among the educated because the word was used in the KJV several times to translate a Heb. word for "serpent." In heraldry, half cock, half serpent. Identified variously with the basilisk and the crocodile.