XXad-er (`akhshubh (Ps 140:3); pethen (Ps 58:4); tsiph`oni (Prov 23:32); shephiphon (Gen 49:17); tsepha` (King James Version margin; Isa 14:29)): This word is used for several Hebrew originals. In each case a poisonous serpent is clearly indicated by the context. It is impossible to tell in any case just what species is meant, but it must be remembered that the English word adder is used very ambiguously. It is from the Anglo-Saxon noedre, a snake or serpent, and is the common English name for Vipera berus, L, the common viper, which is found throughout Europe and northern Asia, though not in Bible lands; but the word "adder" is also used for various snakes, both poisonous and non-poisonous, found in different parts of the world. In America, for instance, both the poisonous moccasin (Ancistrodon) and the harmless hog-nosed snakes (Heterodon) are called adders.
Alfred Ely Day