The Cerastes in Greek myth is a serpent that is incredibly flexible, so much so that it is said to have no spine. It can have either two large ram-like horns or four pairs of smaller horns. The Cerastes hides its head in the sand with only the horns protruding out of the surface; this is meant to deceive other animals into thinking it is food. When the animal approaches the Cerastes, the Cerastes promptly kills it.
The origin of the word is most likely from the Greek word, kerata, meaning horns, and the myth is most likely derived from the habits of the snakes in the genus of the same name, Cerastes. Which are desert dwelling animals, which can have horn-like protrusions over their eyes, and are ambush predators, though not nearly large enough to take prey items much larger than a mouse or small lizard.