This name is derived from the word ‘tirna’ meaning Lord or Master. Five unrelated families of the name arose in Gaelic Ireland, in counties Mayo, Monaghan, Meath, and Tipperary. There are several forms of the name including Tierny, Tearny, Tyernie, and Terney. The first recorded spelling is shown to be that of John Tierny in 1735, obtained from marriage records in County Limerick.
Two of the more prominent families were 1) Ó Tighearnaigh – Uí Fiachrach Muaidhe (Mayo) who were Lords of Carra. It is recoded that clan leader Flann Ó Tighearnaigh, in 1273, was killed in a dispute with the O’Connors and O’Murrays, both of whom had contrived to kill all the Tierneys and assume control of Carra for themselves. Although some Tierneys survived their clan power was greatly diminished. 2) Ó Tigearnaigh – of Brega (Meath). This family claimed descent from Tigernach mac Fócarta (died 865 A.D.) one of the kings of Brega. Tigernach led the Irish to a great victory over the Norse in 848 A.D. They were a branch of the Uí Néills.