Tierney is an Irish surname, and a female given name.
The name is an Anglicized form of the Irish language surname (literally "Descendant of Tiarnach"; historically spelt ), derived from , the Irish word for 'lord' or 'master'. It is sometimes a variant of Tiernan ().
Families
Five unrelated families of the name arose in Gaelic Ireland, in what is now County Clare, County Mayo, County Monaghan, County Meath, and County Tipperary.
Ó Tighearnaigh of Cenél nEógain
This family lived in the territory of Fearnmuigh or Fearnmaigh [which means 'the territory of the plain'], in an area in South Monaghan/South Armagh that is the present Barony of Farney, whose principal town is Carrickmacross.
Ó Tighearnaigh of Uí Fiachrach Muaidhe
This family were Lords of Carra. Almost the only family member recorded in the annals was Flann Ó Tighearnaigh. Gilbert Ó Tigernaig, Bishop of Annaghdown (1306–1323), was also a member of this family.
Ó Tighearnaigh of Brega
This family claimed descent from Tigernach mac Fócartai (died 865), one of the Kings of Brega. They were a branch of the southern Uí Néill. "The Kingdom is said to have stretched from Birr in County Offaly to the Hill of Uishneach in Westmeath. Tighearnach resided at the Great Crannóg of Lagore, which is situated near Ratoath in County Meath, not far from Dublin. Tighearnach led the Irish to a great victory over the Norse Vikings in 848 A.D."