Actually, dr. bill, I believe the greek word means "rattle" or "clapper" (and that Aristophanes used it metaphorically, in the sense you suggest.)

Thus, the scientific name for the "rattlesnake" is Crotalus terrificus, and the active ingredient in its venom is crotoxin.

Edit: apparently dr. bill and I were editing and writing simultaneously. On rechecking, I find that the above-cited are two different types of rattlesnakes.