Kingdom of York in the context of "Kingdom of Dublin"

The Norse–Gaels (Old Irish: Gall-Goídil; Irish: Gall-Ghaeil; Scottish Gaelic: Gall-Gàidheal; Manx: Goal-Gael, 'foreigner-Gaels') were a people of mixed Gaelic and Norse ancestry and culture. They emerged in the Viking Age, when Vikings who settled in Ireland and in Scotland became Gaelicised and intermarried with Gaels. The Norse–Gaels dominated much of the Irish Sea and Scottish Sea regions from the 9th to 12th centuries. They founded the Kingdom of the Isles (which included the Hebrides and the Isle of Man), the Kingdom of Dublin, the Lordship of Galloway (which is named after them), and briefly ruled the Kingdom of York (939–944 AD). The most powerful Norse–Gaelic dynasty were the Uí Ímair or Ivar dynasty.

Over time, the Norse–Gaels became ever more Gaelicised and disappeared as a distinct group. However, they left a lasting influence, especially in the Isle of Man and Outer Hebrides, where most placenames are of Norse–Gaelic origin. Several Scottish clans have Norse–Gaelic roots, such as Clan MacDonald, Clan MacDougall and Clan MacLeod. The elite mercenary warriors known as the gallowglass (gallóglaigh) emerged from these Norse–Gaelic clans and became an important part of Irish warfare. The Viking longship also influenced the Gaelic birlinn and longa fada, which were used extensively until the 17th century. Norse–Gaelic surnames survive today and include MacIvor, MacAskill, and [Mac]Cotter.

Earl of Northumbria or Ealdorman of Northumbria was a title in the late Anglo-Saxon, Anglo-Scandinavian and early Anglo-Norman period in England. The ealdordom was a successor of the Norse Kingdom of York. In the seventh century, the Anglo-Saxon kingdoms of Bernicia and Deira were united in the kingdom of Northumbria, but this was destroyed by the Vikings in 867. Southern Northumbria, the former Deira, then became the Viking kingdom of York, while the rulers of Bamburgh commanded territory roughly equivalent to the northern kingdom of Bernicia. In 1006 Uhtred the Bold, ruler of Bamburgh, by command of Æthelred the Unready became ealdorman in the south, temporarily re-uniting much of the area of Northumbria into a single jurisdiction. Uhtred was murdered in 1016, and Cnut then appointed Eric of Hlathir ealdorman at York, but Uhtred's dynasty held onto Bamburgh. After the Norman Conquest the region was divided into multiple smaller baronies, one of which was the earldom of Northumberland, with others like the earldoms of York and numerous autonomous liberties such as the County Palatine of Durham and Liberty of Tynedale.