You also have to be very cautious, as I'm sure you're aware. Here in Ireland the English came in and transliterated what they 'thought' the locals called places and gave them phonetically English names. The trouble is that in Irish you have so many subtle spellings that the Englishised spellings could have meant any one of several things originally.
The same could be true of any place anywhere where an invading force had influence.
Take your Ball Hill for instance. It could originally have been Bailey Hill and some invaders come along and call it Baal Hill, because that's what they understood from the locals. I'm not claiming this to be the case with this particular hill obviously, just using it as an example.