My late wife used to teach French people English by saying that they already knew some English. They were perplexed until she explained that 40-50% of English derives from French.

The Norman invasion was the best thing that ever happened linguistically to English. Before its grammar was as complex as Icelandic. That got vastly simplified. Also English speakers learned to borrow words easily, not only from French but eventually other languages. For instance, "amok" as in "to run amok" comes from Japanese...

I don't think that your premise is correct, however. We eat mutton because that's how the dish was pronounced, not because of reticence to "eat sheep".