Ó Tighearnaigh
Ó TIGHEARNAIGH—I—O Tierny, O Tearney, O'Tierney, Tierney, Terney, (Tiernan), Lord; 'descendant of Tigearnach' (lordly); the name (1) of a branch of the Cinel Eoghain who were anciently chiefs of Fearnmaigh, in the present Co. Donegal; (2) of a branch of the Ui Fiachrach who were formerly lords of Ceara, now the barony of Carra, in Co. Mayo, and are still numerous in that county; and (3) of a Westmeath family of the southern Ui Neill race. At the end of the 16th century, the name was common also in Clare and Tipperary. The Mayo family is often called Ó Tighearnáin (which see) in Irish and Tiernan in English; and MacFirbis also gives Ó Tighearnáin as an alias for Ó Tighearnaigh of Westmeath.
Alphabetical Index to Irish Surnames