The most famous and powerful of the royal families of Ireland were the O’Neills of Ulster, who enjoyed the High Kingship longest of all; the O’Briens of Munster, the O’Conors of Connaught, the MacMurroughs of Leinster, and the McLaughlins of Meath. Their descendants are simply legion, for all the Irish clansmen were kindred to their kings and chiefs, and assumed, as was their blood right, their surnames when these came into fashion. When the Irish septs, about the end of the tenth century, by the direction of King Brian the Great, chose their family designations, the prefix “Mac” was taken as indicating the son, or some immediate descendant of the monarch, prince, or chief of that particular tribe, while that of “Ui” or “O,” as it is now universally written in English, signified a grandson or some more remote kinsman of the original founder of the name. Thus, the families bearing the prefix “Mac” generally hold that they descend from the elder lines of the royal family, or the leading chiefs, while those who bear the “O” descend from the younger lines. And so it has come to be a national proverb, founded on more than mere fancy, that every Irishman is the descendant of a king. The Irish prefixes, however, are a genuine certificate of nobility, if by that term is meant long descent. An old rhyme puts the matter in homely but logical manner thus: “By ‘Mac’ and ‘O’ you’ll surely know True Irishmen, they say; But if they lack both ‘O’ and ‘Mac’ No Irishmen are they.”