Origin: Mag Oireachtaigh, 'son of Oireachtac' (oireachtac meaning a member of a territorial council under the regional king , involved in treaties and dispositions); a variation of Mag Aireactaig, the name of an ancient and respected Connacht family, of the same stock as the O'Conors. In the 13th. century oireacht (Anglo-Irish 'eraght') is applied to a body of vassal nobles in receipt of a chief's tuarastral, or wages of submission.
Cathal, (or Charles, brother of Teigh Mor who is 102 on the O'Conor pedigree) son of Muirghas, son of Tomaltach, King of Connacht (815 - 836), was the progenitor of the Family of Geraghty of Clan Roduibh. Some were chieftains of Clan Tomaltaigh ( a territory between Balintober and Tulsk) and others of the Muinntear Roduibh territories ( west and along the side of Loch Ree) in County Roscommon. At first the name wasO'Roduibh, of Clan Tomaltaigh and Siol Muredhaigh, chief of Muintair Roduibh, but towards the end of the 12th. century, the descendants of Oireachtac O'Roduibh assumed the Mag Oireachtaigh name. One of them was head chief of the Siol Muiredhaigh, (the territorial and dynastic name of clans descended from Muireadhach Muilleathan of Magh Aei, King of Connacht, son of Fearghus, who died in about 700 A.D.) The territory was located in the central part of the Roscommon and was ruled bythe O'Conor Don and was occupied by several allied septs.
The Mag Oireachtaigh sept's chieftain was one of the 'four royal chiefs' under O'Conor who ruled Connacht and were also high kings of Ireland from time to time. They shared a common ancestry with the O'Conors. As such were closely allied with the them, sharing in each other's battles and territorial claims. O'Conor ruled a confederation of the clans that occupied the Siol Muiredhaigh territory and directly under O'Conor were the four royal chieftains; McGeraghty, O'Flannagan, O'Mulrenhan and O'Finaghty.Each royal chieftains was assigned special honorary duties at official functions. O'Finaghty had the privilege of drinking the first cup at every royal feast, (checking for poison?). O'Murenhan was the royal poet whose duty it was to relate the glorious deeds of O'Conor and the Siol Muireadhaigh. McGeraghty was honoured above the other chieftains and was given special status. At the inauguration of each new O'Conor king, McGeraghtywas given gifts of cattle from the new High King.
After 1404 the Irish Annals make no further mention of the sept. However, in 1585, the Composition Books of Connacht identifies Connor McGirraght as (the last known) chieftain of the sept which at that time was located in O'Kelly's country. There are two theories regarding why the McGeraghty's lost their ancestral land. They may have been expelled by O'Conor from the Siol Muireadhaigh territory after centuries of strife between the two clans, or perhaps the Anglo Irish, (e.g. the Burkes) may have seized the land. In 1235, after a prolonged war of conquest, Richard de Burgh became lord of 25 cantreds of the province of Connacht. The remaining five, near Athlone being reserved for the English King, who immediately leased them for an annual rent to King Felim O'Conor. In 1385 the Siol Muireadhaigh was split between O'Conor Don and O'Conor Roe. In the process, some think that McGeraghty's land holdings must have diminished considerably, or perhaps lost altogether.(The Annals record a bloody battle between O'Conor Roe and Mageraghty, during which Mageraghty's land and dwellings were burned, and the Mageraghty chieftain taken prisoner).
Eventually, having lost their ancestral homeland, which according to O'Conor records was originally comprised of fourty-eight townlands, (about 24,000 acres), some of the clan moved to Mayo and Sligo. (Coincidently, in 1052 the annals record a McGeraghty as chieftain of the Calree tribe in Corran, Sligo).Others moved 19 or 20 miles south of their ancestral homeland to O'Kelly's country of Hy Many where O'Kelly allowed McGeraghty to establish a chieftainship on four townlandsin Fuerty parish on land owned by the bishopric of Elphin. Of the 33 quarters of land in Fuertyparish, McGeraghty was granted four town lands,i.e. Aghgowre, Buniniber, Aghgad and Clinlergin, occupying in all a total of 1,970 acres. O'Kelly as overlord was allowed to take rents of 20 shillings from each under chieftain for each of the townlands they inhabited. This was the last bastion of the remnants of the Mag Oireachtagh clan. They had lost their prestige as the most illustrious ofthe four royal chieftains under O'Conor, and their patrimony was diminished from the fourty-eight townlands they had held in their heyday down to the four townlands they occupied in 1585. Instead of being honoured as the kin of the O'Conors, they were now subservient to O'Kelly, their overlord.
On April 3rd 1653, the town of Roscommon surrendered to Cromwellian forces. Shortly after, the McGeraghty sept which occupied territory close by the town of Roscommon, was dispossessed. In 1666, the Books of Survey and Distribution record that all the quarters of land held by McGeraghty in Fuerty parish were parceled out to Cromwellian supporters. The remnants of the McGeraghty sept followed their kin who had moved to Mayo and Sligo. One group settled on an Island they named Innish Murray, after their Siol Muireadhaigh territory (anglicized as Sil Murray), another group settled near Crough Patrick, where one family later became keepers of the Black Bell of Saint Patrick.
p.s. There are several variations of the coat of arms. The most accepted and probable one is of two falcons, flying above an oak tree, (similar to the one on the O'Conor coat of arms, as if to protect the tree.