The Tain Bo Culaigne

   Then it was that a very bold young warrior of the Ulstermen came nigh the hosts; his bye-name was Oengus son of Oenlam Gabè ('the One-handed Smith'). And he drove the hosts before him from Moda Loga, which at that time was called Lugmud, to Ath da Fert ('the Ford of the Two Gravemounds') in Sliab Fuait.
   What scholars say is: If Oengus son of Oenlam Gabè had fought them in single combat, two-thirds of the host would have fallen before that by him in single battle. Howbeit it was by no means so that they acted, but they attacked him from ambush on every side, till he fell at their hands in unequal fight at Ath da Fert in Sliab Fuait.

   Then came to them Fiacha Fialdana ('the Generous and Intrepid') of the Ulstermen to speak with the son of his mother's sister, namely with Manè Andoè ('the Unslow') of the Connachtmen. And thus he came, and Dubthach Doel ('the Black Tongue') of Ulster with him. It was in this wise that Manè Andoè came, and Dochè son of Maga along with him.
   When now Dochè macMagach espied Fiacha Fialdana, he straightway hurled a spear at him, but so that it went through his own friend, through Dubthach Doel of Ulster. Then Fiacha Fialdana hurled a spear at Dochè macMagach, so that it went through his own friend, through Manè Andoè of Connacht. Thereupon said the men of Erin: "A mishap in throwing," they said, "is what hath happened to the men, for each of them to kill his friend and nearest relation."
   Hence this is entitled Imroll Belaig Eoin ('the Misthrow at Bird-pass'). And 'the Other Misthrow at Bird-pass' is another name for it.

   Then said the men of Erin to Tamon the fool that he should don the garments of Ailill and the king's golden shawl, and go to the ford under their eyes. So he put the garments and golden shawl of Ailill upon him [and he went on to the ford under their eyes.] The men of Erin began to scoff and to shout and jeer at him. "It is a disguising of Tamon ('Stump') for thee, O Tamon the fool" they cried, "with the dress and the golden shawl of Ailill upon thee!"
   When Cuchulain saw him, it seemed to him in his ignorance and lack of knowledge that it was Ailill himself that was there. And he slung a stone from his staff-sling at him so that Tamon the fool was smitten lifeless where he was on the ford. Hence Ath Tamuin ('the Ford of a Stump') is the name of that ford ever since and 'the Disguising of Tamon' is the name of the tale.