“Scotch-Irish” is an American term that became popular in the latter 1800s, referring to the largely Protestant immigrants to the United States originating in the northern Irish province of Ulster. The majority of Scotch-Irish were people intentionally settled in Ulster as a counter to the native Catholic Irish, who immigrated to Ulster from the lowlands of Scotland and the borderlands between England and Scotland.
The Ulster settlers were a solution to depopulation caused by the wars in Ireland, and it was hoped that the Protestant settlers would counterbalance the habitually rebellious Catholic Irish. The regions they came from had a history of violence and poverty. The heritage of violence was thought to have prepared them for withstanding Irish disorder, and poverty made migration to Ulster an attractive proposition. They were deliberately selected by various proprietors, landowners, and King James (1601-1623).
The large number of Ulster immigrants to British American colonies in the 1700s were usually simply called “Irish,” but modern historians prefer the term Scots-Irish, on the grounds that “Scotch” refers to whiskey. This is unnecessarily pedantic, not to mention that Scotch-Irish is deeply embedded in the history books and in American tradition.
During the colonial era, it is estimated that some 200,000 Scotch-Irish migrated to the mainland colonies. How many may have migrated to Canada (British after 1763) or various Caribbean colonies is not well-known. The colonies, particularly Pennsylvania, attracted the Scotch-Irish for several reasons, the most important of which was the ready availability of farmable land, but also, there was no established church (the official and politically dominant religion in Ireland was the Church of England) that discriminated against dissenters such as the Presbyterians.