Etymology Dictionary

ADDER,  a viper. (E.)   M. E. addere, P. Plowman, B. xviii. 352; and again, in P. Plowman, C. xxi. 381, we find 'in persone of an addere,' where other MSS. have a naddere and a neddere.  The word addere is identical with naddere, and the two forms are used interchangeably in Middle English.  [There are several similar instances of the loss of initial n in English, as in the case of auger, umpire, orange, &c.]—A.S. nædre, an adder, snake; Grein, ii. 275. + Du. adder, a viper. + Icel. naðr, naðra. + Goth. nadrs. + O.H.G. natra, G. natter.   ¶ The root is not clear; possibly from ✔NA, to sew, spin, cf. Lat. nere, to spin, so that the original sense may have been 'thread,' 'cord.'   Cf. Old Irish, snáthe, a thread.  See Curtius, i. 393.   Wholly unconnected with A.S. áttor, átor, poison.