Hastings' Dictionary of the Bible (1898)
AD'DER. The word translated thus in various passages of the Bible does not always mean what the English word denotes. 1. In Gen 49:17 it indicates a venomous serpent (perhaps the cerastes, or horned snake) which lurks in the path. The usual habit of the cerastes is "to coil itself on the sand, where it basks in the impress of a camel's footmark, and thence suddenly to dart out on any passing animal.
So great is the terror which its sight inspires in horses, that I have known mine, when I was riding in the Sahara, to suddenly start and rear, trembling and perspiring in every limb, and no persuasions would induce him to proceed. " — Tristram. In Ps 58:4 and Ps 91:13 the Egyptian cobra is probably meant, for it is found in southern Palestine, dwells in holes, is used by snake-charmers, and is very dangerous. This is the animal seen on Egyptian monuments, symbolizing immortality, and always connected with the winged globe.
In the former passage above, there is reference to the fact that there are serpents of some kinds or particular individuals which will not yield to the charmer. " See Asp. Still other kinds of serpents are referred to under this name in Ps 140:3; Prov 23:32 — species of viper, it is thought.