In 658 the Saxons captured the Celtic Eastern Somerset (Somerton) near Circenster and Dorset. Breifne from the eighth century was also known as Uí Briuin Breifne of Cavan because its septs were descendants of the Uí Briuin clans of Connacht of the territory comprised Armagh and Monaghan and parts of Louth, Fermanagh and Down as the territory of Oriel of the Airghialla federation was founded in the fourth century. Branching out of the race of Cian, son of Oilill Olum, the Clan Cian is found anciently in the territory of h-Éile Muman, among other places. The Uí Bruin Cualand and Lords of Uí Mail lived in Wicklow, Leinster and Dublin, Wicklow, Munster as tribes, wherefrom Tallaght is older than the village of Saggart.
The Uí Fiachrach divided into two septs. The descendants of Fiachra, son of Eochaidh Mugmedon, King of Connacht in the fourth century. The more important, northern Uí Fiachrach Muaidhe were located in Co. Sligo-Mayo. The descendants of Indrechtaigh MacMuireadhaigh (Silmurray), a branch of the Ui Briuin, who were settled in Co. Roscommon. The first named inhabitants of Crom Cruach were the Masraighe tribe who ruled Magh Slécht until they were conquered by the Uí Briuin tribe in the 8th century A.D. The descendants of Eoghan, son of Niall of the Nine Hostages in the fifth century, together with his brothers Conall Gulban and Eoghan, conquered the land of north-west Ulster, which was then divided between them Eoghan captured the stronghold at Aileach and his kingdom included the penninsula known as Inishowen (Inish Eoghain), (Tirconnell-Donegal). The Cenél Eoghain were one of the main branches of the Northern Uí Neill. The Tirowen territory comprised Tyrone and part of Derry and Tir Eoghan meaning ‘Eoghan’s country.’
Aengus Mac Nafrach, King of Munster, in the fifth century, enlarged the territories of the Decii by annexing to them the lands of Magh Femin, comprising the present barony of Middlethird, and the large extended plains near Cashel, called Gowlin, together with the country about Clonmel: and from this period the designation of Decie-Thuasgeart, or North Decie, became applied only to his grant; the former territories in Waterford still retaining the distinctive appellation of Decie-Deisgeart, or South Decie. This was a time when the king of Ossory (roughly modern Kilkenny) suddenly appears in the Irish annals as a figure of national importance who rose to power through his strategic alliances with various groups of Vikings. This territory comprised west Waterford near Dungarvan. The Déisi were descendants of Fiacha Suighdhe, brother of High King Conn of the Hundred Battles. They migrated from Tara in the third century and settled in what is now Co. Waterford establishing the territory of Decies. In the seventh century the Osraige chiefs recovered the majority of their territory, and the descendants of Aengus Mac Nafrach regained power in the area. The Déisi Mumhan of Desmond were of Co. Waterford and southern County Tipperary. Septs included Ua Bric (O'Brick), Ua Faeláin (Phelan/Whelan).
The Déise were strongly maritime based in tradition and set up colonies in South Wales. The first king of Demetia (Dyfed), Antonius, was charged with protecting the southern half of Wales in much the same way as Cunedda was given Gwynedd as King of North Wales when Roman authorities asked for the help of Aed Brosc in keeping Irish pirates away from the western coast of Britain. When the last British king died without a male heir, the Déisi were on hand to fill the breach. Desmond territory in South Munster comprised Kerry and Cork. Its creation as a kingdom was thought to occur in the third century, when Oliol Olum, King of Munster, divided his territory between his two sons, giving Desmond to Eoghan, and Thomond to Cormac.
The earlier origins of the Déisi are stated to be on the plains of the River Boyne, where the tribes of the Déisi Brega continued to flourish in early medieval times. The Deisi of Brega and Tara were driven from Waterford city, a Norse foundation and it became Ormond. Much of the metal-work in Waterford to belong to the period, 840s to 880s. County Waterford was the ancient home of Deisi Mumhan, Magh Femin, Uí Liathain and Coscraidh. The Viking settlement of Waterford city was founded in the 9th and 10th centuries. In the twelfth century, the chieftains of the Decii assumed the surname O'Feolain. Viking fleets were sailing on the Suir from the ninth century and from the era of Brian Boru, the Irish high-kings would hire Waterford ships captains to run their navy. The building of those ships represented an enormous community effort: it took 2,650 man days to build each of the great warships.
The Masraige tribe of Leitrim were the inhabitants of Magh Slécht (Cavan and Armagh) at the time of St. Patrick. It was this tribe who supplied the ancient Druids and High Priests of the god Crom Cruaich and their successors the Christian priests. According to Strabo the country of the Belgae extended from the Rhenus (Rhine) to the Liger (Loire). Belgica was one of the four provinces of Gaul near the Rhine, delineated by Augustus. Most Irish rivers have descriptive names, but there are rivers whose names mean nothing in Irish and have been christened by the Firbolgs.
Fermanagh is in North Ireland while all the other neighbouring counties are within the republic. The River Shannon and Lough Allen divide Leitrim into North Leitrim and South Leitrim. Saint Dallan Forgaill, the Chief Ollamh or Poet of Ireland was a member of the tribe. History is vague as to what happened to them. They survived at least until the coming of the Uí Bhriuin in 700 A.D. who then dispossessed them and took control of Tullyhaw. The word Masraige means "Kings of Death", which may be related to their worship of Crom. The High King most connected with the worship of Crom was King Tighernmas. TIGERNMAS; 13th Monarch D. 1543 B.C. Reigned 50 yrs. He won 27 battles against the followers of Heber Fionn. He set up and worshipped the idol "Crom Cruach", in Co. Leitrim and observed centers akin to Stonehenge... Another is Tagharina in Londonderry in the parish of Glendermot. Cromaghs, Cromkill, Cromy, Taggarts Land, Crookedstone appear on Irish gravestone inscriptions.
Again his name means "Lord of Death". There is another standing stone also named Crom Crúaich in Drumcoo townland, County Fermanagh. The Déisi were descendants of Fiacha Suighdhe, brother of High King Conn of the Hundred Battles. They migrated from Tara in the third century and settled in what is now Co. Waterford establishing the territory of Decies. Saint Tirechan's memoir of Saint Patrick, written in 670 A.D. known as the "Breviarium." which is preserved in the "Book of Armagh. Mael Ruiss or Mael Roiss are the same as Mael Rubha, meaning servant or lad of Ruba or Ros, next in importance to Column Cille of the Scottish-Irish Church to Dalriada. Born 640, he became the Abbot of Bangor in Ulster. In 671, Mael Rubha crossed to Alba, founded the monastery of Applecross in 673, and died there in 722 at the age of eighty. Slain by Norsemen at Urquhart, near Conon Bridge. "Ruba" might in fact be a reference to Latin "rubus", meaning 'red'. Mael Rubha is refered to as "the red priest". So his name may reflect his dedication to the people of Ross.