There a whole section on the Scotch Scots topic at Scotch Irish American Scots Irish as a general term and the subsection History of the name Scotch Irish Seems to be explained pretty well Looks like people have gone over the topic repeatedly on the talk page there There s an interesting quote in the section Talk Scotch Irish American More on Scots Irish vs Scotch Irish Apparently the use of Scotch for people while offensive in Scotland is normal in Ulster Personally it doesn t matter to me which term is used It s an interesting example of conflicting usage between America and the British Isles and apparently between Scotland and Northern Ireland too