The Cerastes, a horned snake, is so called because it has horns on its head like a ram (ceras=horn). More-over they are called Kerastes in Greek.
This reptile has four horns, by displaying which, as if they were a kind of bait, it attracts other animals and destroys them. It buries its whole body in the sand, diplaying nothing but it's four horns, by wich means it captures the birds and beasts thus attracted. It's also more twisty than other serpents, so that it looks as if it had no spine*.
*'...dreadfull was the din
excerpt from a twelfth century Bestiary
Of hissing through the hall, thick swarming now
With complicated monsters head and tail,
Scorpion and asp, and amphibaena dire,
Cerastes horned,hydrus and ellop drear,
Milton, Paradise Lost, book X