In 8th century Connacht, the kindreds of the Uí Briúin Bréifne migrated out of their territory of Maigh Seóla (the plain of Seola, which is roughly coterminous with the modern-day barony of Clare in the County Galway) after a great contention arose between them and the other Uí Briúin septs. The Uí Briúin were a royal dynasty of the kingdom of Connacht descended of Brión, who was a 4th century King of Connacht and son of Eochaid Mugmedon, High King of Ireland. Eochaid was a direct descendant of Conn Cétchathach or "Conn of the Hundred Battles", a 2nd century High King for which the Kingdom of Connacht and all of his descendants, known as the Connachta or "Race of Conn" take their name. The fourth great-grandson of Brión was Brénainn mac Fearghna, who died about 576 and is now aligned with a Y-chromosome mutation called "A5902". One of Brenainn's grandsons, Maenach mac Baithin, was an Uí Briúin king recorded in the Annals of Tighernach in 653 after killing an Ui Maine king in Connacht... "The battle of Airther Seola, in which fell Marcán son of Tomán, king of the Uí Maine. Cennfhaeladh son of Colgu and Maonach son of Baithín, king of the Uí Briúin of Brefne, were the victors." The "Cenél Brénainn", or kindred of Brénainn, were a fledgeling tribal group within the greater dynasty of the Uí Briúin Bréifne that, upon their late 8th century migration, all carved out a territory for themselves in the "rough third of Connacht" which became the Kingdom of Breifne, and in modern times was shired in the counties of Leitrim and Cavan. The largest Cenél Brénainn groups: the Teallach Eachach from which the MacGoverns of Tullyhaw descend, and the Teallach Dunchadha from which the MacKiernans of Tullyhunco descend, settled in what is today western Cavan, and fell under the leadership of the dominant Uí Briúin Bréifne sept of the Muintir Ruairc, of which the O'Rourkes, Kings of Breifne, descend. Other septs of the Cenel Brénainn were less-known and somewhat mysterious and in some cases settled elsewhere. However, the extensive genetic research in this group is beginning to shed light on the rest of the Cenel Brenainn. The genealogies in the Book of Ballymote, written in 1390, records the following: "Brenaind son of Fearghna, had two sons, i.e. Baithin and Dubh da crich. Dubh da Chrich had six sons, i.e. Dubhthach, Dobran, Mael Bennachta, Murchadh, Guairi, and Fannan. From Dubhthach are descended the Ui Dubthaigh, from Murchadh are descended the Ui Murchadha, from Guairi are descended the Ui Guairi, from Fannan are descended the Ui Fandan. Baithin, son of Brenaind, had a son Maenach. Maenach had seven sons, i.e. Eochaid, the ancestor of the Tealach Eachath, Dunchadha, the ancestor of the Teallach Dunchadha, Finducan, the ancestor of the Ui Finducan, Braenan, Corcran, Ciarmac and Mael Duin- he was the worst of them because Dallan cursed him." Many of these individuals named are confirmed lineages among A5902+ men with long-established surnames, which at present are the following: A5902>FGC34296 & A5902>FGC59200 are the Teallach Eachdhach. The chiefly line of the MacGoverns are present in A5902>FGC59200>BY18134. As Ballymote states, Eachach is descended of Maenach mac Baithin mac Brenainn, the Ui Briuin king in 653. A5902>FGC55184 are the Teallach Dunchadha. The chiefly line of the MacKiernans are present in A5902>FGC55184>FGC55181>A21793. Dunchadh is also descended of Maenach mac Baithin mac Brenainn. A5902>FT130287 are the Ui Guaire. This kindred settled in Leinster by the 10th century and were lords of the Ui Cuillin in modern-day southern Co. Kildare. The Book of Ballymote names Guaire as a son of Dubh-da-Crich mac Brenainn. The Annals of the Four Masters records two of the Ui Guaire: "962. Cairbre Ua Guaire, head of the hospitality of Leinster, died." "1032. Tadhg Ua Guaire, lord of Ui-Cuilinn, was slain by the son of Mael-na-mBo." A5902>FTC14661>FT101173 are the Ui Dubhthaigh, a ecclesiastical family who became very numerous in Connacht and the midlands. The Book of Ballymote names Dubhthaigh as a son of Dubh-da-Crich mac Brenainn. A5902>FTC14661>FT195045 are the Ui Murchadha, and the surnames present within this clade indicate a long presence in Breifne. Ballymote has Murchadh descended of Dubh-da-Crich mac Brenainn. A5902>BY100917 are the Ui Fannan, who are numerous in modern-day County Roscommon and may have been associated with the Ui Briuin Ai or settled in their territory of Machaire Connacht. Fannan is named in Ballymote as a son of Dubh-da-Crich mac Brenainn. A secondary source, "Bethada Náem nÉrenn" also mentions Dubh-da-Crich's sons in a poem about the Life of Saint Maedoc, that is Máedóc of Ferns, being fostered by the Ui Dubhthaigh as a child. "He was given to be fostered and nurtured by Úa Dubthaig, that is Dubthach son of Dub-da-Crich, &c. And this Dubthach was one of six sons of Dub-da-Crich... Six sons of Dub-da-Crich renowned, Dubthach, Dogran of the bright countenance, Maelbennachtadh, beauteous Murchad, Guaire, and Fannan of the curly hair." The location given of this fosterage is Magh Slécht, which lies in Tullyhaw, County Cavan. However Saint Maedoc's date of birth is said to be 558ad, generations before Dubhthaigh mac Dubh-da-crich would have lived and centuries before our kindreds migrated out of Maigh Seola in western Connacht. Historians suggest that Saint Máedóc of Ferns' life details are a conflation of several different individuals who lived at different times. However regardless of this, it points to the Ui Dubhthaigh being firmly planted where the Teallach Eachdhach and Teallach Dunchadha settled in the 8th c. It may be the case that all the kindreds of Brénainn were at one time in the vicinity of Magh Slécht, meaning "the grave-strewn plain" which was anglicized "Moyslaught" and lies in the southeastern portion of the barony of Tullyhaw, adjoining that of the barony of Tullyhunco in the County Cavan. There are many other surnames present in these kin-groups aside from their confirmed ancestor, as surnames were very fluid in medieval Ireland. Sometimes new surnames developed on certain lines as individuals took the name of a father or another more recent ancestor after their surname had been long-established. There is also the numerous cases of "Non-Paternal" or "Surname-Change" Events, which could have occurred with upwards of more than 50% of Irish men and there were many reasons for this outside being an illegitimate son or orphan. It was possible for one to become "detached" from his lineage and just known by a patronymic (given name-mac-father's name) which went on for generations until there was another surname established. The gaelic custom of fosterage created alias-surnames which many men were known by in their adult lives. Another large factor are the Scottish mercenary kindreds recruiting Irish men in the tuaths in which they were settled and employed from c1250 to c1600. Among the Teallach Dunchadha is a group of MacLeans from the light-infantry "Redshanks" who were employed by O'Rourke in the late 15th century, as well as another group of MacLeans among the Ui Guaire, from a kin-group of this clan that came under the employ of Gerald FitzGerald, the 9th Earl of Kildare in the early 16th century. Among the Ui Fannan is a MacDonnell, the name of one of the earliest and most numerous galloglass families that came into Ireland in the early 14th century as hired heavy-infantry.