Source: The Medieval Bestiary
The cockatrice or basilisk is a mythical heraldic beast described in bestiaries as being hatched from a rooster’s egg by a toad, with a serpent’s head and tail.[1] The basilisk always has the body of a snake, but the cockatrice has the feet and wings of a cockerel.[2][a]The cockatrice is sometimes depicted as having the wings of a dragon.[2] The creature’s most distinctive characteristic is its ability to kill with a stare; there are several tales in British folklore of cunning heroes overcoming a cockatrice by tricking it into looking at its own reflection.[3]
Late-medieval bestiaries claimed that the weasel is the only animal immune to the gaze of a cockatrice.[4] It was also said that a cockatrice would die instantly upon hearing a rooster crow.[5]
The Oxford English Dictionary gives a derivation from the Anglo-Norman word cocatrice, itself derived from the medieval Latin calcatrix, a translation of the Greek word ichneumon, meaning tracker, the name given to an animal revered by the Ancient Egyptians for destroying the eggs of the Nile crocodile.[6]