Quote Originally Posted by slohairt View Post
Exactly. Not all Northern Protestants were of Planter stock, some were native Irish who converted. Also, there was a Scottish presence in Ulster long before the Plantation: The Gallowglass. As they were Gaelic-speaking and Catholic, they were assimilated into the local populace even faster than the Normans a couple of centuries prior.
Gaelic Irish that converted to become protestants mainly joined the Church of Ireland, which is a branch of the Anglican church, aka Episcopalian. This was the established church. OTOH, protestant Ulster Scots were and are mostly Presbyterian, so it's not all that hard to disambiguate two groups that attended different churches. The main reason for conversion was to overcome bans on Catholics buying land and/or joining the learned professions, which were repealed in the first half of the 19th century.