Brittonic

Brython, Brittonic, Brythonic. The branch of the Celtic languages that includes Welsh, Breton, and Cornish, the modern survivors of the P-Celts; distinguish from Goídel, Goidelic, and Q-Celts (Irish, Scottish Gaelic, and Manx). The terms ‘Brython’, ‘Brythonic’, were coined by Sir John Rhy$[hacek]s (1840–1915) to denote the Brittones, Romanized Britons in post-Roman times. Recent usage favours Brythonic for parent languages, Brittonic for modern languages.

A Dictionary of Celtic Mythology. James McKillop. Oxford University Press, 1998.