[1] The concept is mainly relevant outside of England, Ireland, Scotland and Wales, particularly in Australia, but is also used in Canada, the United States, New Zealand and South Africa, where a significant diaspora is located.
Anglo-, meaning English[2] is derived from the Angles, a Germanic people who settled in Britain (mainly in what is now England) in the middle of the first millennium.
[3] Celtic,[4] in this context, refers to the people of Ireland, Scotland, Wales, Brittany, the Isle of Man and Cornwall.
In an 1869 publication, the term was contrasted with Anglo-Saxon as a more appropriate term for people of English, Irish, Scottish and Welsh descent worldwide: "Anglo-Saxon," as applied to the modern British people, and Britannic race, I believe every impartial scholar will agree with me in thinking a gross misnomer.
[6] Use in this term can be seen in a 1914 Irish unionist ballad: The United Anglo-Celtic Isles Will e'er be blessed by Freedoms smiles No tyrant can our homes subdue While Britons to the Celts are true.