As I understand it, the various bits of medieval England could barely agree on units among each other. "England" is named after the Angles, one of the Germanic

As I understand it, the various bits of medieval England could barely agree on units among each other. "England" is named after the Angles, one of the Germanic tribes that showed up and settled down in England after Roman rule ended. They brought their own proto-Germanic language with them and displaced the local languages- and to some extent people too. French was a comparatively small addition, it contributed a lot of vocabulary and spelling and so on, less so grammar. The Norman invasion was not a lot of actual people- enough to staff up a new aristocratic class speaking French, not enough to displace the local language or people so much.