A curious number of Southern Appalachians like to refer to themselves or extended family members as being "Black Irish".

There are Facebook discussion groups catering to Appalachian Americans (with tens of thousands of members), and almost weekly an "expert" pops up assuring other members that the "Black Irish" are a thing, and that thing is usually this:

"Loads of Irish people have black eyes, dark hair and skin.  They come from Spanish sailors stranded on Irish coasts during the naval retreat of the Spanish Armada in 1588.  These sailors intermarried with local Irish girls." 

This oft-repeated folk history - and the assertion that large sections of the native Irish population are dark in complexion due to this - is utter claptrap.