Erenaghs' and 'coarbs' functioned as stewards, collecting rents and tithes. This revenue went to the rector and vicar of each parish, the bishop and the erenagh himself, who spent some on the maintenance of the church buildings. The area of Derry called Kilrea which was a compact little parish lying along the River Bann, and like its neighbor Agivey, held a peculiar position being "appropryated" to the Abbey of SS. Peter and Paul of Armagh. The connection between the O'Diamond's and the Abbey at Kilrea is described in a inquisition taken in 1609 - "Two acres of Glebe land, and also the Parish of Kilrea, containing ten ballibows, whereon are both a parson and vicar, for the space of 170 years past, have pertained to the Abbot of SS. Peter and Paul of Armagh; and like wise the tithes were paid unto the said Abbot and his predecessors; and that the said presentation and right of patronage, together with said tithes of Kilreagh. lately came to the crown by the said Abbot was "seized in his demesne as of fee, in right of his house. of and in the four townlands called Kilreagh in possession of the herenagh O'Diamond, and two parts of the tithes thereof, and of and in the tithes for the fishing for eels near adjoining the same, and also of and in the two townlands called Monaghgrane, with the tithes thereof in the parish of Kilreagh, aforesaid." From the name of the erenagh or layman who farmed the property and had the upkeep of the Church, the place was nominated " Kilrea O'Demon, or O'Diamond. -from the O'Cahans Princes of Ulster.
The O'Deas are mentioned several times in the "Annals of the Four Masters" as the coarb families who administered the termon lands attached to many of the local churches, especially the important monastic settlement at Dysart O'Dea. They are also known for having supplied several candidates to the local clergy and some bishops to the adjoining dioceses. Among the most notable was Archdeacon Cornelius O'Dea who was consecrated Bishop of Limerick in 1400. In 1568 the Bishop of Kilmacduagh, Conor O'Dea drew up an interesting lease when he bequested the banqueting hall and castle of Dysart to his nephews, Diarmuid Óg and Donnchadh, and the two gardens and round tower to Domhnall O'Dea.
The 1659 Census of Ireland shows seven O’Dyman families in Loughinsholin-listed under principal Irish names. In 1719 Bryan, Felix, and Henry O’Dymond were listed as tenants on Hertford Estate, Lisburn, County Antrim. In County Londonderry the greatest concentration of Dimond’s was located in the Barony of Loughinsholin in the Parish of Ballyscullion followed by adjoining Tamlaght O’Crilly.
In 1663 there were native O’Diamond’s recorded in Maghera Parish. Parish of Maghera is a rectory in the province of Armagh and diocese of Derry. The ancient and modern name of this parish is compounded of Magher-na-dra 'the field of vespers'. It is bounded on the north by the parishes of Errigal and Desertoghill, on the east by Tamlaght O'Crilly and Ballyscullion, on the south by Magherafelt, Termoneeny, Desertmartin and Kilcronaghan, and on the west by Ballynascreen, Dungiven, Killelagh, and Upper and Lower Cumber. -Ordnance Survey, April 1830, Lieutenant R.J. Stotherd
The 1740 Census of Barony of Loughhisholin lists five O’Diamond’s and recorded as Protestant. From the name of the erenagh or layman who farmed the property and had the upkeep of the Church, the place was nominated "Kilrea O'Demon, or O'Diamond.
The Donegal Presbytery was it's neighbor to the north. This area spawned two major immigrations during the 1700s: one to western Pennsylvania and the other to North Carolina. These were not opposite directions in those days. In each case pioneers from the Wedge had to head northwest along the Susquehanna and pick up the Great Wagon Trail [Native American Warrior's Path] at Lancaster. Pennsylvania. From here the pioneers could struggle over the mountains into western Pennsylvania or follow the Great Wagon Trail southwest into the Valley of Virginia and on into North Carolina. Note that both western Pennsylvania and North Carolina are the areas where the Diamond/Dimond colonial family groups of Irish descent originate.