Section 1. Lineage of McOsker, McCusker, McCosker, MacOscair

 A) (Documented) McOsker is probably a branch of The Maguires.

 Rev. Peadar Livingstone (1932–1987) was a Roman Catholic priest.  Fr. Livingstone was a renowned scholar in both the Irish language and local history. In 1969, he published The Fermanagh Story, a comprehensive history of the county of Fermanagh.

 "McCUSKER (Mac Oscair) : The McCuskers of Fermanagh were probably a branch of the Maguires. The name had established itself at least as early as the beginning of the seventeenth century, as is seen in a pardon given to 'Tir-Roegh McPatrick McCosker of Fermanagh -- husbandman, Coll McPatrick McCosker of same, Edmund McHugh McCusker of same -- labourer'. Besides, there is a Carrowvickosker (Carrickmacosker) townland mentioned in the Plantation grant  to Conor Rua Maguire in Magherasteffany."

     From Peadar Livingstone's The Fermanagh Story.


 B) (Clarification) The name Carrowvickosker, translates not as carrick = rock, but as carrow = quarterland. The 'Carrick' in Carrickmacosker is a mistranslation of  'Caeathrar' anglicé Carrow, meaning a 'quarter'. (In other words, this was McCusker's quarter of the ballybetagh. A ballybetagh seems to amount to 960 acres.) Carrow does not indicate the presence of settlement but it does imply land tenure by the MacOskers. (From a messageboard “Study on Place Names in Ireland”, by Shane Anderson, Yale University.)

 C) (See Maps at this link) There is currently a Carrickmacosker townland in Co. Fermanagh, and it is comprised of about 239 acres. (about ¼ of the earlier mentioned 960 acre ballybetagh) Most townlands were named between the 12th and 16th century. It was in the 1600s that they became mapped and defined by the English administration for the purpose of portioning the land for investors or grants. Carrickmacosker is a current nameplace, but has had other names over the centuries. The earliest we have found is CorMcCosker, in 1609. Cor translates to “a round hill”. See the Carrickmacosker link for copies of maps showing this.

D) (Assumption) We believe McOsker and McCusker can be genetically traced to a common ancestor Donn Carragh Mag Uidhir, born in 1264 A.D. We need family members to assist in this project. See the DNA section of this website for more information on this.

E) (Documented) Donn Carragh Mag Uidhir is considered the first Lord of Fermanagh. Uidhir is pronounced “Uwarr”, so Mag Uidhir means “Son of Uidhir”, and sounds like McGuire. Donn Carragh is the common ancestor of McGuire, McGwire, Maguire, etc.

 F) (Documented) The Annals of Ulster (compiled in the late 15th century) states the following. "Matthew, son of Oscar Mag Uidhir, rested in Christ on the 14th of the Kalends of November, and his brother John, son of Oscar was killed on the same day. Oscar, son of Art, son of Flaherty (Flaithbertach) Mag Uidhir, son of Donn Carragh Mag Uidhir.”

G) (Documented) The original Irish text of the Annals of Ulster reads "Matha mac Osgair Megh Uidhir, quieuit in Christo, decimo quarto Kalendas Nouembris, a derbrathair idon Seaan mac Oscair do marbadh isin lo cetna."

 H) (Speculation) Oscar was a potentially important player in the senior Maguire line at the time, as would presumably have been his sons. It is reasonable to assume Matthew and/or John were possibly the stewards of the land now referred to as Carrickmacosker, and around that time changed the family surname to MacOscair (Son of Oscar) (or at least some variant.)

I) (Speculation) Researchers at Queen's University in Belfast believe it is more likely Carrickmacosker was named for Maurice, archdeacon of Clogher, son of Matthew, son of Oscar Mag Uidhir. (See additional information on this at the Carrickmacosker page.)

J) (Seeking Clarification) Another reference "Mac Cusker, -Cusker : Principally a branch of the MacGuires in Fermanagh, centered at Ballymacosker," from Edward MacLysaght's The Surnames of Ireland. I have seen this reference numerous times on family tree websites, but have never found evidence that Ballymacosker ever existed. (Bally translates to "Town") I assume that MacLysaght mis-spoke, and actually meant “centered at Carrickmacosker” which does exist on both current and centuries-old maps. If anybody has evidence of the existence of a Ballymacosker, please forward it to us.


We will continue to update this as our research continues.

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