Old English nædre 'serpent, adder', of Germanic origin; related to Dutch adder and German Natter. The initial n was lost in Middle English by wrong division of a naddre; compare with apron, auger, and umpire.

• One of the words Anglo-Saxons used for a snake was naedre, which became nadder in medieval times. At some point during the 14th or 15th century the word managed to lose its initial n, as people heard ‘a nadder’ and misinterpreted this as ‘an adder’. A northern dialect form nedder still exists. A similar process of ‘wrong division’ took place with words such as apron and umpire (see pair), and the opposite can happen too, as with, for example, newt and nickname. In time adder became the term for a specific poisonous snake, also known as the viper. The same change nearly happened to the word aunt (Middle English) (which comes from Latin amitia ‘aunt’), for between the 13th and 17th centuries ‘mine aunt’ can appear as ‘my naunt’. In France this change has happened: the word was ante in Old French, but is now tante through the running together of ta ‘your’ and ante. See also deaf.