The islands would have something that eventually became (regional) Gaelic. But the Normans did a good job killing most of these people and replacing them with pale people
If people were there 8000 years ago, this part didn’t happen until your time period
I think it’s saying that it’s the oldest word that English speakers today use which might not be true
So looking it up, the Yiddish word comes from an old German word and is around 1000 to 1500 years old. This makes a lot more sense and is in the time period for when they started killing Gaelic people