Adder may be derived from Brittonic*ador, *edir or Old Englishedre, possible ancient hydronymic terms derived from an Indo-European formation meaning "a watercourse, a channel" (compare River Etherow). The possibility of the name deriving from Old English ǣdre, "a vein" (Anglianēdre), or *ǣdre, meaning "quickly" is objected on the grounds that these would have maintained the long initial vowel in English and Scots.
Also suggested is derivation from Gaelicfad dûr, meaning "long water". though the Gaelic was never spoken in the Scottish southeast.
Course
The stream wends its way south east for approximately 5km (3.1mi) where it joins with the Faseny Water to form the Whiteadder Reservoir created in 1968, which supplies most of the towns of East Lothian (including, before its closure, the Cockenzie power station) and Berwickshire, with water.
In the 12th century, Melrose Abbey established granges for its sheep flocks at Penshiel, Hartside, Edmundston and Friardykes in the catchment of the Whiteadder, leading to disputes over grazing rights with the tenants of the Earl of Dunbar.
Notability
Fishing
The Whiteadder provides recreational salmon and troutfishing. A number of angling clubs offer access to the river, including the Whiteadder Angling Association (trout) and Berwick and District Angling Association (salmon, sea trout and wild brown trout). The Whiteadder is the home of the oldest Angling Club in the world verified by the Guinness Book of Records, Ellem Angling Club, established in 1829. The regalia of the club is on display at Paxton House in Berwickshire. It is also the site of Ninewells, the childhood home of David Hume.
Natural heritage
The lowermost section of the Whiteadder is a Site of Special Scientific Interest (SSSI) by virtue of its water crowfoot, salmon, lamprey and moulting mute swan.
Shale crags along the Whiteadder (April 2006)
Whiteadder Water and Roughside Wood from the road into Greenburn (February 2007)
Whiteadder, downstream from Ellemford Bridge (February 2007)
Whiteadder Water after heavy rainfall, depicting runoff from the peat in the Lammermuir Hills (July 2007)
Whiteadder Water running around Abbey St Bathans (March 2010)