The Scots-Irish

Scots-Irish is an ethnic group from Ireland which ultimately traces its roots back to settlers from Scotland, and to a lesser extent, England. In particular Scots-Irish can often be traced back to the Scottish Highlands, Scottish Lowlands, Galloway, and the Scottish Borders.
The Scots-Irish and their descendants are primarily found in Ulster, where they are Ulster Scots, and in Canada and the USA, laterly where they are often identified as Scotch-Irish. Most Scots in Ireland are Ulster Scots, although there are also some who live in the Republic of Ireland, mainly in Donegal.
The Scots-Irish are strongly identified with Protestantism and, in modern day Ireland, unionism.
The Ulster-Scots are predominantly Presbyterian, with many Anglicans, some Congregationalists, and some Quakers. In America, many Scots-Irish people gravitated towards the Methodist and Baptist denominations. In Ireland, Ulster Scots are usually identified with the Irish unionist tradition, although many Ulster-Scots involved themselves in the Society of United Irishmen, an Irish republican organisation in the late 1790s.

(Source: Wikipedia)