Recorded as O'Tiernan, MacTiernan, McTiernan, and Tiernan, this notable surname is Irish. It derives from the Old Gaelic name MacTighearnain, meaning the son of Tierna, a name meaning lord or master. Traditionally, Irish family names are taken from the heads of tribes, revered elders, or some illustrious warrior, and are usually prefixed by "Mac", denoting "son of", or "O", grandson, male descendant of. Two separate septs of MacTiernan arose independently in Ireland, the first belonged to the Ulster county of Cavan, and were a branch of the great O'Rourkes, styled Lords of Breffny, whose chieftains ruled territory in Counties Cavan and Leitrim. No less than thirty-three MacTiernans are mentioned in the Annals of the Four masters, several of them Chiefs of Teallach Donnchadha (modern Tullyhunco, in County Cavan). The name is still widely found in the Cavan-Leitrim area, usually without the prefix "Mac". The second sept of MacTiernan belonged to the north-eastern part of County Roscommon, where they held territory in medieval times. This sept was descended from Tiernan, grandson of Turlough Mor O'Connor, High King of Ireland (1119 - 1156). Twenty-six persons of the name are known to have arrived at the port of New York as Irish famine immigrants during the years 1846 - 1851; among them James Tiernan, aged 18 yrs., who embarked from Liverpool on the ship "Queen-of-the-West", on April 11th 1846. A Coat of Arms granted to the Tiernan family is an ermines shield with two red lions passant. The first recorded spelling of the family name is shown to be that of MacThighearnain, of County Cavan, which was dated circa 1250, in the "Annals of the Four Masters", during the reign of King Henry 111 of England, known as "The Frenchman", 1216 - 1272. 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.