Star Trek: 10 Things You Didn't Know About Miles O'Brien
6. He's Royalty
Miles O'Brien was no ordinary man. He was directly descended from Irish Royalty. He was the descendant of the High King Brian Boru himself. Bar Association sees O'Brien and Bashir add the Battle Of Clontarf to their holographic repertoire, which for history buffs and Irish fans was seriously cool to see.
The Battle of Clontarf took place on the 23rd of April 1014 in Dublin, Ireland. Brian Boru led an army against a Norse-Irish army and a Viking Army. By the end of the battle, almost all of the major commanders - including Boru himself - would be dead, but Boru's forces were successful in driving back their opponents.
Boru, while King of Munster, established the O'Brien Dynasty in Ireland. After Boru's death, the Ó Brian's (the earlier spelling) would continue to hold the seat (including another High King of Ireland) until Munster was partitioned, wherein they became the Kings of Thomond, a seat they held for roughly five hundred years.
The name O'Brien is a popular one still in Ireland, so it is very gratifying to see that not only does it survive into the 24th century, but that a man of such importance is keeping the station afloat.