That's an old and popular idea, but controversial in modern linguistics. See for example http://anglisztika.uni-eger.hu/public/uploads/orsi-2015_576cfe9171530.

That's an old and popular idea, but controversial in modern linguistics. See for example http://anglisztika.uni-eger.hu/public/uploads/orsi-2015_576cfe9171530.pdf http://anglisztika.uni-eger.hu/public/uploads/orsi-2015_576c... which among other things points out that words like "beef" and "mutton" don't appear in English until centuries after the Conquest.