Medb's Men, or, The Battle of the Boyne
Book of Lecan, 351b-353a

A king took kingship over Ireland once on a time, i.e. Eochaid Feidleach, the son of Finn, the son of Rogen Ruad, the son of Easamain Eamnab of the seed of Rifad Scot from the tower of Nimrod; for it is of the race of Rifad Scot was every invasion which seized Ireland except Cesair only. It is therefore he was called Eochaid Feidleach, because he was ‘feidil' to all, i.e. ‘righteous’ towards all was that king.

He had four sons, namely, the three Findeamnad (‘eamain’ meaning ‘a thing which is not divided’), and they were born of one birth, Breas, Nár, and Lothar their names; it is they who made Lugaid-of-the-three-red-stripes with their own sister the night before giving the Battle of Druicriad to their father. The three of them fell there by Eochaid Feidleach; and it was Eochaid Feidleach who made the holy request that no son should rule Ireland after his father for ever, and that was verified) ; and Conall Anglondach, the son of Eochaid Feidleach,. from whom are the Conailli,h in the land of the men of Breagh. That king, Eochaid Feidleach, had a great family,’ namely, e, daughter of Eochy, wife of Fergal mac Magach; from her Bri Eili in Leinster takes its name; after Fergal she was wife to Sraibgend mac Niuil of the Erna, and she bore him a son, Mata the son of Sraibgend, the father of Ailill mac Mata; and Mumain Etanchaithrech, daughter of Eochaid Feidleach, wife of Conchobar mac Fachtna Fathach, the mother of Glaisne Conchobar’s son; and Eithne, daughter of Eochaid Feidleach, another wife of the same Conchobar, mother of Furbaide Conchobar’s son; (it is therefore he was called ‘Furbaide’ because the ‘urbad’ or ‘cutting’ of him out of the womb of his mother was performed after she was drowned in the stream Bearramain, which is called the Eithne today, and it is from her the river takes its name, namely, Eithne, and Diarmaid was Furbaide’s (first) name); and Clothra, daughter of Eochaid Feidleach, mother of Cormac Conloingeas, Conchobar’s son (or Nessa daughter of Eochaid Sulbaide was the mother of Cormac Conloingeas); and Deirbriu, daughter of Eochaid Feidleach, from whom were (called) the pigs of Deirbriu; and Meadb of Cruachan, daughter of Eochaid Feidleach, another of Conchobar’s wives, mother of Amalgad, Conchobar’s son, so that Conchobar was Meadb’s first husband, and Meadb forsook Conchobar through pride of mind, and went to Tara, where was the High-King of Ireland. The reason that the High-King of Ireland gave these daughters to Conchobar was that it was by Eochaid Feidleach that Fachtna Fathach had fallen in the battle of Lettir-ruad in the Corann, so that it was as his eric these were given to him, together with the forcible seizure of the kingship of Ulster, over Clan Rudraidhe: and the first cause of the stirring up of the Cattle-raid of Cuailngne was the desertion of Conchobar by Meadb against his will. Tindi, the son of Conra Cas, of the Fir Domnand, was king of Connacht at that time, and Eochaid Dala and Fidig mac Feicc, of the Gamanraidi, were laying claimc (?) to the kingship.

Fidig mac Feicc goes to Tara to assemble the kings for himself, and he asked Meadb of Eochaid Feidleach. Tindi, Conra’s son, got word of this story, and lay in ambush for Fideic. They met over the Shannon streams, and the children of Conra and Monodar, Conra’s son, slew Fidig, and that was the first reason of the war between the children of Conra and the Gamanraidi. Eochaid Feidleach executed a prince’s injustice on Tindi, drove him into the deserts of Connacht, and set Meadb up in the royal seat of Cruachan. It fell out, however, that Tindi was a visitor (?)d with Meadb for a long time after that, so that it was in Cruachan with Meadb the fairs of Ireland were wont to be held, and the sons of the kings of Ireland used to be in Cruachan with Meadb at that time to see if they might exchange war with the province of Conchobar. (Amongst these) came Sraibgend mac Niuil of the Erna, and his son, Mata mac Sraibgind, to Meadb to see if they could make war on Conchobar for all the ill-feeling that was between them. The festival of Tara was held by Eochaid Feidleach, with the provinces of Ireland about him (all) except Meadb and Tindi. The men of Ireland bade Eochaid bring Meadb to the gathering. Eochaid sent Searbluath, his female messenger, to Cruachan for Meadb. Meadb goes on the morrow to Tara, and the fair-races were run by them for a fortnight and a month. Thereafter the men of Ireland disperse. Conchobar stayed after the others in the fair, watching Meadb, and, as Meadb happened to go to the Boyne to bathe, Conchobar met her there, overcame her, and violated her. When that tale was told in Tara, the kings of Ireland rose forth from Tara, and Tindi mac Conrach and Eochaid Dala with them. Another version says that Eochaid Dala had fallen by Tindi before that (in a dispute) about the kingship, but that is not true.

The banners of the king of Ireland are raised to attack the king of Ulster; and Tindi, the son of Conra, challenged Conchobar to fight. Conchobar accepted that; and Monodar Mór, son of Conra and brother of Tindi, who happened to be with Conchobar at that time, was asked to check Tindi. He said that he would do so, and they had a champion’s fight; Tindi fell in the conflict, and everyone said, “Good is the deed"; and the Druid said, “Mac Ceacht shall be his name for ever”; hence “Mac Eacht” adhered to him.

Conchobar won the battle on the Boyne over Eochaid Feidleach; and Sraibgend mac Niuil and his son fell there, sustaining the battle. Eochaid Dala took up the yoke of battle across Meath, over the green-streamed Shannon, and brought Meadb and Connacht safe with him through dint of fighting, so that he was not dared from the Boyne to the Shannon. The Fir Domnand and the Dal n-Druithni and the Firchraibi, from whom sprang Eochaid Dala, came to Cruachan after the slaying of Tindi, the son of Conra Cas, for though they were three tribes through division they were one tribe by origin, namely the children of Genand, the son of Dil(?), the son of Loch, and they were Firbolg by race. The counsel they decided on was to appoint Eochaid Dala to the kingship of Connacht with the consent of Meadb. Meadb consents to that on condition that he should marry her, and that he should have neither jealousy, fear, nor niggardliness, for it was ‘geis’ to her to marry a man who should have these three qualities. Eochaid Dala was crowned through this, and was a while in Cruachan, as Meadb’s husband. At that time Ailill the son of Mata, the son of Sraibgend of the Erna, came to Cruachan, and Ailill was then a young child, and the remnant of Sraibgend’s children were along with him that they might be reared by Meadb, because of Meadb’s relationship to him, i.e. Ele, the daughter of Eochaid Feidleach, was his grandmother. Ailill is reared in Cruachan after that until he was a great spirited warrior in battles and in conflicts, and a battle-sustaining tower against Conchobar, defending the province of Meadb, so that it was he who was chief of Meadb’s household afterwards, and Meadb loved him for his virtues, and he was united to her, and became her lover in place of Eochaid Dala. Eochaid Dala grew jealous because of this, and all the Fir Domnand shared in his jealousy through affection, so that they thought to banish Ailill, and all the Erna who were with him, out of Connacht; but Meadb did not permit the doing of that deed, for she loved Ailill better than Eochaid. When Eochaid saw Meadb’s partiality, he challenged Ailill to fight for the kingdom and his wife. They fought a fierce fight, and Eochaid Dala fell in that conflict by Ailill mac Mata through the wiles (?) of Meadb. Ailill assumed the kingship of Connacht thereafter, with the consent of Meadb; and it is he who was king of Connacht at the time of the crowning of Conaire the Great and the beginning of the cattle-raid against the Ultonians. It was to that Ailill that Meadb bore the Maines, and Maine was not their first name but thus: Feidlimid, i.e. Maine Aithreamail, and Cairpri, Maine Maithreamail, and Eochaid, Maine Andoe, and Fergus, Maine Tai, and Ceat, Maine (M)or(g)or, and Sin, Maine Milscothach, and .Daire, Maine Mo-epert.

Why are they called the Maines? Not difficult. Of a day that Meadb was at the gathering of Cluitheamnach and happened to be preparing for the battle of Findchorad against Conchohar, she said to her Druid, “By whom of my children shall Conchobar fall?" quoth she. “Thou hast not borne them yet, unless they be rechristened,” quoth the Druid. “Anyhow, it is by Maine he shall fall.” And it is for that reason she called each of her sons Maine, in the hope that Conchobar might fall by him; and these nicknames superseded their real names. Meadb thought that it was Conchobar, the son of Fachtna Fathach, whom the Druid meant. It was not he, however, but Conchobar, the son of Arthur, the son of Bruide, the son of Dungal, the son of the king of Scotland, from across the water. He it was who fell there by Maine Andai, the son of Ailill and Meadb.

SOURCE
O'Neill, Joseph. "Cath Boinde." Eriu. v.2 pp.173-185.