Pollnagollum 911
My Y-DNA has confirmed that my oldest ancestor to be found buried in Ireland was Pollnagollum 911.  No one knows what his name was, he is called Pollnagollum 911 while there are many burial Cairns near the Pollnagollum Cave in what is today modern Co Fermanagh in Northern Ireland, Pollnagollum 911 was one of three found buried inside the cave. 

Pollnagollum 911 lived 3000 years before surnames came in use in Ireland so he isn't an O'Kelley or anything else but he is my ancestor as well as the ancestor of a great many other people who go by many different surnames.  My R-DF13 DNA matches indicate that Pollagollum 911's ancestors lived in the Yorkshire England area perhaps 200 years before his birth.

Pollnagollum died about 2195 BCC more than 4000 years ago.       

+2 ii.  Treanmacurtagh