The Heffernans are descended from Milesius, King of Galacia in Spain, through the line of Heber (Eber), his son. Heber became the first Milesian king of Ireland in 1699 bc, ruling jointly with his brother Heremon (Eremon). Heber died a year later and Eremon ruled for another 14 years.
        The Dalcassian Clan was known for its fierceness in battle and was a major force with Brian Boru in wiping out the Vikings. (Which very nearly wiped out the Dalcassians.)
        The Heffernans are more directly descended from Cormac Cas, the grandson of Owen the Great who won half of Ireland from Conn of the Hundred Battles.
        The Clan of Heffernan originally inhabited a territory near Corofin, County Clare, called Muintirifernain [People of Ifernain] after them. They established themselves in eastern County Limerick on the Tipperary border and were Chiefs there of Owneybeg, where after a period of time they were displaced by the Ryans.
        The old manuscripts, such as the Book of Rights, describe the O'Heffernans as one of the four tribes of Owney, the others being MacKeogh, O'Loingsigh (Lynch) and O'Calahan. The two most distinguished memebers of the Heffernans were Aeneas OHeffernan who was the Bishop Of Emily, 1543-1553, and William Dall OHeffernan (1715-1802), Gaelic poet.
        The original text of this quote is here.