English people are descended from various admixtures of Anglo-Saxons (various Germanic tribes from modern day Denmark and north Germany), the Britonnic Celts wh

English people are descended from various admixtures of Anglo-Saxons (various Germanic tribes from modern day Denmark and north Germany), the Britonnic Celts who lived there under the Roman Empire before the empire collapsed and the Anglo-Saxons came, Norsemen (who are hard to genetically distinguish from Anglo-Saxons since they come from very similar North Germanic populations separated by only a few centuries; at any rate they conquered a large chunk of northern England that became known as the “Danelaw”) and possibly Normans (who were also Norsemen with maybe some admixture from the other populations in they ruled over in Normandy, though I’m not sure how large of a population transfer came along with that particular conquest compared with the others). The Britonnic Celts in the western highlands of the former Roman Britain were not easily or immediately conquered by the Anglo-Saxons. Hence, the Anglo-Saxon name for Britonnic Celts eventually became the modern English word “Welsh”. Though note that the Anglo-Saxon term “Wealh” would not have merely referred to the people of modern Wales in particular; any Britonnic Celt was a “Wealh”, hence the other Celtic homeland of Cornwall.