Who were the Cumbrians?

The Anglo-Saxon Chronicle in Latin uses the term Cumbri for the people it describes in Old English as Strecledwalas ­ [7]. These were the Strathclyde Welsh.  The word Welsh is an Anglo-Saxon term for a Briton - the people who inhabited the island of Britain when the Germanic tribes first arrived here. We see the term in the names Wales and Cornwall. In their own language, the Britons had first called themselves Brythoniaid and their language Brythoneg - the Bretons still call their language Brezhoneg which is this term exactly.  Later, in Wales and Cumbria the Britons (though not in Cornwall or Brittany) took to calling themselves Cymry or perhaps in Cumbria Cömbri  -  meaning something like "The Compatriots" or simply  "Our Folk".

Edmonds sees the emergence of this terminology  as happening around the 10th Century when the rulers of the Cumbrians saw themselves and their people as still a separate ethnic group [7].

In Camden's Britannia in 1586, Camden visited Cumberland and says "…Cumberland; in Latin Cumbria [and in Saxon Cumbraland and Cumer-land]… It had the name from the Inhabitants; who were the true and genuine Britons and called themselves in their own language Kumbria or Kambri."  He goes on to give examples of names of places which are purely British in language such as Caer-luel, Caer-dronoc, Pen-rith, Pen-rodoc.

The political heartland of the Cumbrian kingdom was around Glasgow, with royal centres at Partick (Pertig) and then Govan (Gofan), (I give names in my best guess at their Cumbric original and a Welsh speaker will see dialectal differences from Welsh) but it possibly extended up towards Clach nam Breatann (The Britons' Stone) past the northern end of Loch Lomond. Its see was at Glasgow (Glasgau) and its "patron saint" was St Kentigern or Mungo. Cumbric place names extend west into Ayrshire (Strad Aeron), and it may have controlled Carrick (Cerrig?) for a while. Cumbric place-names are common in Lanarkshire (Llanerc), West and Mid Lothian (Lleuddion), Peebles (Pebyll), extending south down the Clyde  (Clud) Valley into Nithsdale (Strad Nidd) and Dumfries (Dinpres) and south past Carlisle (Caer Lywel) into Allerdale and south to where Copeland has Cumbric names as far south as Ravenglass (Rhenglas), then east across towards Penrith (Penrhudd or Penrhed) and down the Eden Valley to Mallerstang (Meilfre) and the traditional south eastern boundary on Stainmore.

David's Inquisition shows that he considered South East Scotland including Teviotdale as being within the bounds of the Kingdom of Cumbria. However, Cumbric place-names are not very common in that area. Edmonds cites Dauvit Brown's view that this area was given to the Cumbrian kings after they supported the Scots to defeat the Northumbrians at the Battle of Carham in 1018, at which  the Cumbrian king Owen the Bald was killed.  

By the time David I became Prince of the Cumbrians in 1113, the Principality was not wholly Cumbric speaking. In the prologue to his Inquisition he says that people from different nations lived there and these would be ethnically English, Gaels, Norse people as well as the Cumbrian Britons.  David I was an Anglo-Norman, despite his descent from the Gaelic kings of Alba. 

The English counties of Cumberland and Westmorland were created in 1176-7 [6] and persisted until they were absorbed into the modern county of Cumbria in 1974.