The story of Tallaind Etair (the Siege of Howth) is contained in the12th century manuscript of the Book of Leinster. A central character is Aithirne Ailgeasach of Ulster, a hard, merciless man and a powerful druid and file (poet). His cruel nature was demonstrated when he called on Eochaidh Mac Luchta, a one-eyed king of South Connaught. After being offered any gift he desired, Aithirne asked for Eochaidh’s good eye. The king plucked it out himself and placed it in Aithirne’s palm, and, on washing the empty socket in the nearby lake, the waters turned red with the blood. To this day, the lake is known by the name Loch Deirgdhearc (lake of the red eye), or in English as Lough Derg.
Aithirne moved on then to Ard Brestine, in Carlow, where he spent twelve months as guest of Mes Gegra, the king of Leinster. At the end of his year, he took away with him the wives of 150 of the princes and nobles of Leinster. Although the men of Leinster could not wrong the druid within their own territory, no such prohibition existed once he left their boundary, and so, as he crossed the river Tolka, he was pursued by the angry Leinstermen. An army arrived from Ulster intent on protecting their druid and a mighty battle ensued, where the men of Ulster were routed.
They fled to Howth with Aithirne in their midst, taking shelter in the fort of Dun Bo. Nine days they were there, nine days without food and without water, while Aithirne refused to allow any to taste the healing milk of the seven hundred cattle he had in the middle of the fort. For nine days the armies fought at Dun Bo, until the death of the Ulster champion Mesdead, a foster son of Cuchulainn. Spurred on by the sound of his foster-son’s death cry, Cuchulainn led a fierce attack and broke the resistance of the enemy. The retreating Leinstermen had the presence of mind to raise a red wall behind them, as the warriors of Ulster were prohibited from passing over a red wall. That “red wall” can be seen today as a red sandbank opposite the station house just east of the DART terminus.
One of the Ulstermen, however, was able to breach the red wall, the hero Conall Cearnach. Two of his brothers had been killed by Mes Gegra and he had sworn vengeance. He followed Mes Gegra as far as Clane, Co Kildare, where he killed and beheaded the Leinster king. He removed the brain and baked it with lime, making a sling missile that was known as a “brain-ball”. This brain-ball was later used to kill the Ulster king Conor Mac Nessa. As a footnote, Queen Medb of Connacht was also killed by a brain-ball while bathing in a pool on Inchcleraun Island. Just off the shore of Lough Ree, Inchcleraun is named after Clothra, the mother of Crimthann Nia Nar who had his royal dun or fort on Tower Hill in Howth.
Father John Shearman, an antiquarian who was a priest in Howth, wrote in 1868 that:
“This tale speaks of a hollow, or “gap” beside the Dun, called “Cucullin’s Gap,” from the feats of bravery there performed by that hero. To find out this precise place was for some time a difficult endeavour, as there were many places about the harbour called by that name. An old man at last turned up whose grandfather lived under Dunboe before modern innovations changed its appearance. He remembered a hollow, through which in wet seasons some water flowed, leading up from the sea where Mr. Crosbey’s new store is erected. The depression of the land behind Evora-house on Dunboe grew deeper as it reached the sea in this place. The old Dublin road crossed it where now the new road leads from Abbey- street to the railway station; the hollow was then filled to level it up to its present height This, my informant told me, was called ” the Gap,” and that he often heard his grandfather speak of a battle that was fought there ” about cows.” These traditions must have great value in settling the precise locality of the scene of the “Siege of Howth.” The top of Dunboe was crowned with a moat— portions of it can be still seen. It was a favourite spot in the olden time as a look- out station for the seamen of Howth. On it, too, were lighted the mid- summer fires, which were visible through the whole of Fingal. To the west of the moat at the mearing of the demesne was a terminal cross, to which the funeral processions of the lower part of the town were marched before interment in the old cemetery. Dunboe has suffered much by recent innovations: to make “The new road,” more than forty feet of its flank were cut away some years ago. Still earlier, another slice was cut away to give room for the road at the top of the harbour. Some rocks in this place under the Court-house (now being built), called “Molly Piles Rocks,” anciently defended its base from the fury of the sea in the .north-east gales. Then also the place now occupied by the St. Lawrence Hotel was a deep pool of water, so that the hill was surrounded on the east, north, and west sides with the sea. Dunboe seems destined for still further ruin: an immense hole is made on its side. A house is to be built into it, which, apart from the questionable taste of removing an ancient land-mark of history, will be anything but ornamental to the only approach to the town.”