I really do wonder why it's Gallod and not Callod! Some letters in Welsh 'mutate' - they change depending on what words they're following. For example, Cardiff is Caerdydd, but in Cardiff is yng Nghaerdydd, which is easier to pronounce than it looks. But Callod is the starting word, so why would it be mutated? XD Perhaps it doesn't mean stalk at all and is just a meaningless name.
It is fun to sit there and make funny sounds, though :)