The idea of a correct spelling for a place name or a surname is very much a 20th century phenomenon and before that, especially in Ireland, there was no consistency. Names were spelled phonetically and each variation was down to the whim of the particular person (often an official) recording the information. With family names you will see the spelling change all the time as the records go back. This doesn’t normally represent a particular decision to alter the spelling. Not everyone was literate any way, but even when they were, it simply wasn’t something they bothered about then. The addition or loss of an e or an s in a name, or dropping the O’ or Mac prefixes were also very common.