Origins of the English How is it that the Celtic language was completely replaced even if the people remained — schopenhauer1
I've thought about this one for some time.
France gets its name from the Franks, another Germanic tribe. The consequences for the language were that German words for military ranks and cavalry equipment. They surrendered their language completely
In Britain there is an assumption that before Caesar the country was fully "Celtic", and that after the Romans fled the entire country in a very short time, changed to Anglo-Saxon with Celtic remaining only in place names.
Geoffrey of Monmouth talks about only a handful of invading ships!
I've always entertained the view that Saxon migration started long before the legions left in 401AD. And that Rome purposely invited Saxons to settle in the SE to avoid the problems of raiding along "Saxon Shore". I also made myself unpopular by suggesting that germanic was even spoken in Britain before the Romans invaded. So tribes such as the Belgae and Trinovantes, , Regnenses having Latinised names may well have been Germanic or Celtic speakers. There is simply no evidence as no historical account takes any particular interest in their linguistic origins. The Belgae for example were know to have been recent migrants to Britain and the assumption they spoke Celtic has no basis in evidence.
Languages have no specific boundaries in any event. English is a melange of influences and we have no direct evidence about what the multitude of ethnic groups' influences were.
Early history - protohistory is built on assumptions and those assumptions were largely built on an interest in racialism.
As a side note. Celticism was invented in the 17thC. The Romans never referred to inhabitants of Gaul or Britain as "Celtic". by Contrast early archaeological evidence of so-called "celts" were Germanic. The Halstatt and La Tene cultures were from Germany!
But the contemporary evidence of "Keltoi" (a Greek word BTW) puts Kelts in Massilia southern France, and they are described as Blonde Haired and Blue Eyed.
The idea that the entire continent of Europe was "Celtic" is meaningless.