Irish families as septs of Highland Clans

[O'Callaghan]

If it comes to that, I have Hart in my family tree, and the English, Irish and Scottish Harts are all unrelated. The Scottish Harts have their own tartan, but are not considered to be a clan, or even a sept of one, AFAIK. By default, my Hart family is probably of English origin, but all the world tends to move to London, so that is by no means certain.

There are other names in my family tree that might be septs of Scottish clans, if they were only of Scots origin, but they probably aren't. I am sure there are, for example, Americans, who proudly wear a particular tartan because they have people in their family tree who bore a certain name that appears on a sept list, blissfully unaware that their ancestors were unrelated English people with the same name.

OTOH, the Callaghan was one of the small number of Irish clan chiefs that were actually recognised by the Irish government, that is, until they stopped doing that. The Irish constitution specifically prohibits recognising titles of nobility, so it was probably unconstitutional anyway!