Ath Cliath Cualann (Dublin)
Prose Dindsenchas

Hurdles of wattling the Leinstermen made in the reign of Mesgegra under the feet of the sheep of Athirne the Importunate when delivering them to Dun Etair at the place in which Allainn Etair was taken from Ulster's warriors, where also Mesdedad son of Amergin fell by the hand of Mesgegra king of Leinster. So from those hurdles "Ath Cliath" ("the Ford of Hurdles") was named.

Or thus: "Ath Cliath": When the men of Erin broke the limbs of the Matae, the monster that was slain on the Liacc Benn in the Brug of Mac Oc, they threw it limb by limb into the Boyne, and its shinbone (colptha) got to Inber Colptha ("the estuary of the Boyne"), whence "Inber Colptha" is said, and the hurdle (clíath) of its frame (i.e., its breast) went along the sea following the coast of Ireland until it reached yon ford (áth); whence "Ath Cliath" is said.

SOURCE:
Ancient Irish Tales. ed. and trans. by Tom P. Cross & Clark Harris Slover. NY: Henry Holt & Co., 1936