I've noticed (and posted here) that spelling of placenames can and do change with time. I was surprised to find this even applies to "good/reliable" references like Ordnance Survey Maps that I for one used to think of as almost "gospel". However, particularly for the first editions, no doubt these relied on the literacy skills of the Army engineers performing the Surveys not to mention the local people who's information they were presumably using, and even then they were open to possible transcription errors.