A brief historical note :- Brian Boru was High King of Ireland and was said to have been murdered in his tent in 1014 by a fleeing Viking mercenary, Brodir, after Brian's side had been victorious in the Battle of Clontarf, now a suburb of Ireland's capital city, Dublin. Popular legend credits Brian Boru with evicting the Vikings from Ireland as a result of this battle, but the reality was that this battle was part of a protracted Irish civil war, with Irish and Viking participants on both sides, the opposing side in this particular battle being led by Sigtrygg Silkbeard, often called "Sitric", the Viking ruler of Dublin. Brian's son, Murchad was also killed in the battle. Ironically, due to a quite complicated series of past alliances and marital relations, one of Brian's marriages had been to Sitric's mother! He was reputed to have had 4 wives in all.
The descendants of Brian Boru were called "Ua Brian" and from this evolved the modern Irish sirname of O'Brien.
Finally, I have often seen the tune "Brian Boru's March" being listed as "The March of the High King" on various recordings by Irish artists and groups on their LPs, Audio tapes, and CDs.
Best regards,
Gweltas1 (in Cornwall,UK)