adder

Etymology 1

From Middle English nadder, addere, rebracketing of “a naddere” as “an addere”, from Old English nǣdre (“snake”), from Proto-West Germanic *nadrā, from Proto-Germanic *nadrǭ, from pre-Germanic *néh₁treh₂, variant of Proto-Indo-European *n̥h₁trih₂, from *(s)neh₁- (“to spin, twist”) See also West Frisian njirre, Dutch adder, German Natter, Otter; also Welsh neidr, Latin natrīx (“watersnake”), Dutch naaien.

noun

1. (obsolete) Any snake.
2. A name loosely applied to various snakes more or less resembling the viper.
   1. (chiefly Britain) A small venomous serpent of the genus Vipera
      These include the county's [Cumbria's] only venomous snake - the adder - which relies on exposed elements to successfully breed its young. August 25 2021, Nick Brodrick, “Flourishing Flora and Fauna”, in RAIL, number 938, page 51
      1. The common European adder (Vipera berus).
   2. The puff adders, of Africa (genus Bitis).
   3. (US, Canada) Any of several small nonvenomous snakes resembling adders
      1. Lampropeltis triangulum (milk snake).
      2. Heterodon spp. (hog-nosed snakes), a genus of harmless colubrid snakes found in North America
   4. Certain venomous snakes resembling other adders
      1. Acanthophis spp. (death adders), elapid snakes found in Southeast Asia and Australia
      2. Agkistrodon contortrix mokasen, the northern copperhead, a venomous viper found in the eastern United States
   5. A sea stickleback or adder fish (Spinachia spinachia).

Etymology 2

From add + -er.

noun

1. Someone who or something which performs arithmetic addition; a machine for adding numbers.
2. An electronic device that adds voltages, currents or frequencies.
3. Something which adds or increases.
   They sought out cost adders with an eye toward eliminating them.