Quote Originally Posted by slohairt View Post
A Fhaol Liath,

I would say your etymology is more or less correct. The first Celtic element, bre (Goidelic brí, Brythonic bre) does indeed mean hill. However, it can also mean high and in this case I think that is probably more accurate. The Anglo-Saxon don/dun/den element means hill as well. Since naming a place hill-hill seems rather silly, I would suggest it likely means high hill.
There are quite a few British surnames that come from the words for the same thing in 2 different languages, such as Cheatwood. It isn't at all uncommon.