Tierney is an English-Anglicized surname and given name, derived from the Irish Tighearnach. The name ultimately originates from the Old Irish Tigernach, which comes from the element tigerna meaning “lord” or “master”. As a first name, Tierney is primarily used as a feminine given name in modern times, while its historical roots are masculine through the saintly bearer. Etymology and Origins The root name Tighearnach was borne by a 6th-century Irish saint, the founder of the monastery at Clones in County Monaghan. According to hagiographic accounts, he was captured by British pirates in his youth and taken to the monastery of Rosnat, but he eventually escaped and returned to Ireland. The name was also used as an Irish surname, typically as the Anglicized form of Ó Tiarnaigh (“descendant of Tiarnach”); in Old Irish it appears as Tigernach or Tigernán (a diminutive). Historical Families Five unrelated Gaelic families bore the surname or a variant in different parts of Ireland. One family of the Ó Tighearnaigh (spelled Ó Tighearnaigh) belonged to the Cenél nEógain kindred and lived in the territory of Fearnmuigh (Farney), now the barony of Farney in south Monaghan and south Armagh, with its chief town at Carrickmacross. Another family of the Ó Tighearnaigh was based in the Uí Fiachrach Muaidhe region and were Lords of Carra in County Mayo. One notable bearer recorded in the Irish annals is Flann Ó Tighearnaigh. The other three families were located in County Clare, County Meath, and County Tipperary. The surname variant Tiarnán (or Tiernan) sometimes overlaps as a related form. Modern Usage Today, Tierney is predominantly a feminine first name, though it originated from a masculine-rooted name. Its usage as a given name outside Ireland rose partly due to celebrities such as actress Maura Tierney. The name is also found as a patronymic surname in Irish-speaking regions. Key Facts Meaning: “Lord”, derived from Old Irish tigerna. Origin: Irish (Anglicized form of Tighearnach / Ó Tiarnaigh). Type: First name (also used as a surname). Usage Regions: Ireland and the English-speaking world. Related Names: Tighearnach, Tiarnach, Tighearnán, Tigernach (Old Irish forms); Tiernan (variant).