The Clan/Sept History

According to ancient Irish manuscripts, the name Cinnsealach (later anglicized to Kinsella) first came into being in the year 365 AD. The occasion was a battle between the King of Tara, Eochaidh Muighmheadhon, and Eanna, King of Leinster.
The battle was fought at a place called Croghan Hill and was decisively won by King Eanna. Near the end of the battle, Eochaidh Muighmheadhon's druid, Ceadnathach, was taken prisoner and brought to Eanna who was standing on the Hill amidst the dissipating battle. Upon seeing Eanna, the druid said, "Thou wouldst never conquer from this hill on which I am, if I were to live." Upon this Eanna transfixed him with his spear; and, as the spear pierced his body, a laugh broke forth from Eanna. "Alas," said the druid, "that is a foul laugh, and it is this that will be given as a name to thy posterity after thee for ever".