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.
Initial text from 1911 encyclopedia -- Please update as needed
An adder is an electronic device that adds three bits. One that adds only two bits is a half-adder.