I often feel like I would understand a lot more names if I bothered learning Welsh. It's pretty popular for made up climbing route names too, because Wales is so good for it I guess. Allegedly some of the classics in the Avon gorge are Welsh derived but I could never figure them out to be sure.

There is a river Avon in England. Welsh at least (inst. celtae) has a noun for "river" which is "afon".