Adder

An adder is a name for the common viper (Vipera cevus), ranging from Wales to Saghalien island, and from Caithness to the north of Spain. The puff-adder (Bitis s. Echidna arietans) of nearly the whole of Africa, and the death-adder (Acanthophis antarcticus) from Australia to the Moluccas, are both very poisonous.

Etymology: The word was in Old Eng. noedre, later nadder or naddre; in the 14th century a nadder was, like a napron, wrongly divided into an adder. It appears with the generic meaning of serpent in the older forms of many Teutonic languages, cf. Old High Ger. natra; Goth. nadrs. It is thus used in the Old English version of the Christian Scriptures for the devil, the serpent of Genesis.

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Initial text from 1911 encyclopedia -- Please update as needed

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An adder is an electronic device that adds three bits. One that adds only two bits is a half-adder.