This interesting surname, widespread in the Ulster County of Tyrone, is an Anglicized form of two distinct Gaelic Irish septs names, O' Caireallain and O' Cearbhallain. The former sept was located in Clondermot, County Derry, where its leader was chief of Clan Diarmada, whence the name of the parish of Clondermot. The sept of O' Cearbhallain was also of Ulster, being located chiefly in Cavan and Monaghan, prior to their migration into the north Leinster county of Meath. Traditionally, Irish family names are take either from the heads of tribes or from illustrious warriors, and are usually prefixed by "mac" meaning "son of", or "o", male descendant of. In this case, the personal bynames "Cearbhallan" and "Caireallan" share the same root i.e., "cearb" meaning hacking, and implying a fierce warrior. Further Anglicized forms of the above two ancient Ulster surnames include Carolan, Carlan, Carland, and Kirlin, On June 18th 1865 the birth of Patrick, son of James Carlin and Sarah McBride, was recorded in Omagh, County Tyrone. The first recorded spelling of the family name is shown to be that of Hugh O' Carolan, Bishop of Clogher, which was dated 1535-1563, in "Medieval Ecclesiastical Records of Co. Donegal", during the reign of King Henry V111, known as "Bluff King Hal", 1509 - 1547. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.