[Ir., of the Long Side].
Daughter of the great king Cathaír Mór, she is described as the queen of two other kings of different generations. In most Old Irish writing she is the wife of Conn Cétchathach [of the Hundred Battles]. Her marriage was thought beneficial to the kingdom; until her death the fields gave three harvests a year. In Esnada Tige Buchet [The Melodies of Buchet's House] Eithne is in fosterage to Buchet when she spends a night with Cormac mac Airt, Conn's grandson, to conceive Cairbre Lifechair; and she appears to be Cormac's wife in Echtrae Cormaic [The Adventure of Cormac].