This family claimed descent from Tigernach mac Fócartai (died 865), one of the Kings of Brega.
"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."[2] A family of the name resided in Ormond, now County Tipperary.
[2] New research now confirms that this family was indeed an indigenous sept. Their seat was in the townland of Park and their lands, Fearann Ó Tighearnaigh, took in most of the present-day townlands of Ballymackey, Ballyknockane, Carrowea, Clash, Falleen, Gortnadrumman, Kilgorteen and Knockane.