"scotch-irish" is a traditional term for ulster scots who later emigrated to what is now the united states; "scots-irish" is a more recent form of the american term, the term has usually been scotch-irish in america, as evident in merriam-webster dictionaries, where the term scotch-irish is recorded from 1744, while scots-irish is not recorded until 1972. and is not to be confused with irish-scots, i.e., recent irish immigrants to scotland.