The sept of Heffernan originally inhabited a territory near Corofin, Co. Clare, called Muintirifernáin after them. Very early, however, they established themselves in Eastern Co. Limerick on the Tipperary border and were chiefs there of Owneybeg, whence they were in due course displaced by the Ryans. The principal families of the name did not migrate very far since Carew tells us that they were among the most important in the Barony of Clanwilliam in 1600. The rank and file remained undisturbed and it is in Counties Tipperary and Limerick they are most numerous to-day. 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, Ó Loingsigh (Lynch) and O'Calahan. The two most distinguished members of the sept were Aeneas O'Heffernan, Bishop of Emily, 1543-1553, and William Dall O'Heffernan (1715-1802), Gaelic poet. The prefix O, discarded during the period of Gaelic submergence, has not been resumed in modern times except in very few cases. Hiffernan is an alternate spelling of the name. The most notable so called was Dr. Paul Hiffernan (1719-1777), the dramatist.