Rath Crinna
Rath Crinna, whence the name? Not hard to say: from Crinna son of Conn the hundred-fighter, who was slain there by Eochaid find Fuathnairt, it was named. Eochaid brought his head with him to the house of Tara and set it on a stake of rowan, to spite Art son of Conn, for that was a thing forbidden to him. For that cause Eochaid was banished into Leinster, and hence come the Fotharta in Leinster to-day. Crinna son of Conn, stout his spear: Dun Crinna was his stronghold: though it is called by his name, short was his span of life therein.
Source:
Metrical Dindshenchas. ed and trans. Edward Gwynn. 1925. Dublin: Dublin Institute for Advanced Studies: 1991.