Adda was the third known ruler of the Anglo-Saxon Kingdom of Bernicia.
Adda was one of several sons born to Ida, the first ruler of Bernicia, as was his successor Æthelric.
Adda may have been the Bernician commander at the battle of Caer Greu, where the British kings Peredur and Gwrgi of Ebrauc were killed. There is some confusion here because of a conflict between sources. The Annales Cambriae state that the Battle of Caer Greu took place in 580. The evidence for Adda being the Bernician king in question is that the Welsh Triads identify that leader as Ida. Since the sources agree that Ida died in 559, it is assumed that the Triads have named Ida by mistake, and that Adda—the only son with a name similar to Ida's -- was meant. However, the Historia Brittonum states that Adda only reigned for 8 years after Ida, in which case either the Bernician leader must have been one of Adda's successors, or else one of the sources has the dates confused. It is also possible that Ælle of Deira led the Angles at Caer Greu—certainly, Ebrauc ceased to exist as a British kingdom after the battle, with Deira taking over its territory. Since, however, the surviving northern British kingdoms subsequently combined to launch a vigorous campaign directed against Bernicia rather than Deira, this suggests that Bernicia was the original combatant.
Bernicia (Old English: Bernice, Beornice; Latin: Bernicia) was an Anglo-Saxon kingdom established by Anglian settlers of the 6th century in what is now southeastern Scotland and North East England.
The Anglian territory of Bernicia was approximately equivalent to the modern English counties of Northumberland and Durham, and the Scottish counties of Berwickshire and East Lothian, stretching from the Forth to the Tees. In the early 7th century, it merged with its southern neighbour, Deira, to form the kingdom of Northumbria and its borders subsequently expanded considerably.
Bernicia is mentioned in the 9th-century Historia Brittonum (§ 61) under the Welsh name of Berneich or Birneich and in Old Welsh poetry and elsewhere under the name of Bryneich or Brynaich. This may reflect the name of a preceding Brittonic kingdom or province, which was subsequently adopted by the Anglian settlers and rendered as Bernice or Beornice in the Old English tongue. If such forms represent a Welsh version of Bernicia, it is unclear why Welsh would need to borrow a foreign name for the area, so the former hypothesis is usually accepted, although no etymological analysis has produced a consensus. The etymology which is most widely cited is that tentatively proposed by Kenneth H. Jackson, which gives the meaning "Land of the Mountain Passes" or "Land of the Gaps". The earlier derivation from the tribal name of the Brigantes has been dismissed as linguistically unsound. In 1997 John T. Koch suggested the conflation of a probable primary form *Bernech with the native form *Brïγent for the old civitas Brigantum as a result of Anglian expansion in that territory during the 7th century.
Bernicia could mean: