Suibne mac Cináeda also known as Suibne son of Cinaeth in some works, was a king of the Norse-Gaels

Norse-Gaels

The Norse–Gaels were a people who dominated much of the Irish Sea region, including the Isle of Man, and western Scotland for a part of the Middle Ages; they were of Gaelic and Scandinavian origin and as a whole exhibited a great deal of Gaelic and Norse cultural syncretism...

 (Gall-Gáedil). His death is recorded by the Annals of Ulster

Annals of Ulster

The Annals of Ulster are annals of medieval Ireland. The entries span the years between AD 431 to AD 1540. The entries up to AD 1489 were compiled in the late 15th century by the scribe Ruaidhrí Ó Luinín, under his patron Cathal Óg Mac Maghnusa on the island of Belle Isle on Lough Erne in the...

Suibne son of Cinaed, king of the Gallgaedil, died

and the Annals of Tigernach

Annals of Tigernach

The Annals of Tigernach is a chronicle probably originating in Clonmacnoise, Ireland. The language is a mixture of Latin and Old and Middle Irish....

 in 1034.

Although sometimes associated with Galloway

Galloway

Galloway is an area in southwestern Scotland. It usually refers to the former counties of Wigtownshire and Kirkcudbrightshire...

, which may possibly derived from the Gall-Gáedil, he is possibly the eponym

Eponym

An eponym is the name of a person or thing, whether real or fictitious, after which a particular place, tribe, era, discovery, or other item is named or thought to be named...

ous ancestor of the MacSween Clan

Clan Sweeney

Clan Sweeney is an Irish clan of Scottish origin. The clan did not permanently settle in Ireland before the beginning of the 14th century, when they became Gallowglass soldiers for the O'Donnell dynasty of Tyrconnell...

 (MacSuibhne) who were found in Knapdale

Knapdale

Knapdale forms a rural district of Argyll and Bute in the Scottish Highlands, adjoining Kintyre to the south, and divided from the rest of Argyll to the north by the Crinan Canal. It includes two parishes, North Knapdale and South Knapdale....

, in the area of Loch Sween  where Castle Sween

Castle Sween

Castle Sween is located on the eastern shore of Loch Sween, in Knapdale, on the west coast of Argyll, Scotland. Castle Sween is thought to be one of the earliest stone castles built in Scotland, having been built sometime in the late twelfth century...

 was built in the 12th century.

If Suibne was ruler of Galloway, nothing is known of his reign at present, nor of his successors. Indeed it is not until Fergus of Galloway

Fergus of Galloway

Fergus of Galloway was King, or Lord, of Galloway from an unknown date , until his death in 1161. He was the founder of that "sub-kingdom," the resurrector of the Bishopric of Whithorn, the patron of new abbeys , and much else besides...

 (ruled c. 1120–1161) that records are properly kept.

Some interpretations of placename evidence suggests his kingdom stretched over modern day Galloway, Carrick, and Nithsdale

Nithsdale

Nithsdale , also known by its anglicised gaelic name Strathnith or Stranit, is the valley of the River Nith in Scotland, and the name of the region...

, perhaps even into upper Douglasdale (ref. Companion).