Common Brythonic is today survived in place-names. “The best example is perhaps that of the River(s) Avon, which comes from the Brittonic abona which translates into “river” (compare Welsh afon, Cornish avon, Irish (and Scottish Gaelic) abhainn, Manx awin, Breton aven; the Latin cognate is amnis).”
The non-place-name evidence lies in stone carvings – most of which are said to be ancient curses.
The British language receded in many Northern and Eastern areas of the lands below the Scottish Highlands throughout the first milennium CE but ceased to exist completely after the battle of Deorham in the 9th century when Cornwall [West Walia] and Wales [North Walia] were cut off from one another. This was shortly after many of British residents of the Cornish penisula had travelled across the sea to Britanny [Amorica] – owing to the reason that despite them being three seperate language in their own right, Cornish, Welsh and Breton share a huge amount of basic vocabulary with one another.
Predictions for 1-20 in British:
- oinos (m) / oinā (f) / oinom (n)
- dewou (m) / dewī (f) / dou (?)
- trīs (m) / tiserīs (f)
- petwār (m) / petiserīs (f) / petuar (?)
Common Britonnic – via Wikipedia