The Irish Gaelic for Wallace or Walsh is "Breathnac i.e. British as in Ancient Celtic British who occupied most of the middle land of the mainland Britain with "Clach nam Breatan" a large stone half way up Loch Lomond side and Dum Barton "Dun Breatan" Fort of the Britons on the Clyde seeming to be the Northern boundary. Rochdale in the English Midlands was originally the Roman town of Regedham (Reged was a British King/Ruler whose Fort in Wigtownshire Scotland gave the local village it's present name of Dunragit)The Welsh Gaelic name gives us Cymry as in The Cumbraes (Islands in the Clyde)and Cumbernauld in Scotland, Cumbria and Cumberland in North England. There is growing proof that Arthur belonged to this area i.e the BORDERS. after repeated invasion by Angles Saxons Scots and Vikings the native British stock either assimilated into the incomers or Migrated to the hills i.e the Highlands, Galloway, Wales and Cornwall and of course then to Brittany on the Northern French coast taking with them their folk legends, hence the reason that the original legends of Arthur came back from Brittany and Cornwall. There is even speculation that some of them finished up in North America via the Orkneys,Iceland,Greenland but that's another story.

I'm afraid I ramble on a bit but old place names and their origins are one of my favourite subjects as are names of people. I'm quite sure that there is still a lot of history to be found in the old place names, unfortunately a lot of them are either becoming forgotten or miss-used and miss-spelt i.e. a village near Stranraer is called Stoneykirk, pretty straight forward you would think but there are no stones nearby. Local pronunciation is Staneykirk which again seems O.K but the truth is it was dedicated to St. Stephen, locally shortened to Stein hence Steinykirk. English cartographers naturally tried to make it English but were wrong. I am in agreement with Tom about the dna test I think there has been some done but I can't remember much about it.
I wonder too about Caledonia and even the Caldees a religeous group as a source of our name.