Gaulish language
The Gaulish language is thought to have survived into the 6th century in France, despite considerable Romanization of the local material culture. Coexisting with Latin, Gaulish helped shape the Vulgar Latin dialects that developed into French, with effects including loanwords and calques (including "oui", the word for "yes"), sound changes, and influences in conjugation and word order. Today, the last redoubt of Celtic language in France can be found in the northwestern region of Brittany, although this is not the result of a survival of Gaulish language but of a 5th-century AD migration of Brythonic speaking Celts from Britain.