The name is often connected with the anglicized surname Mackesy, O'Mackesy, O'Mackesey, Mackessy, Macassy, Macasey, Maxey, M'Asey, M'Assie and M'Casey etc.
Being intertwined with legendary, and semi-legendary stories and characters, often differing greatly, their record of descent has likely been altered over the years for political reasons as was common of many Irish tribes, making it difficult to accurately trace their roots.
[10] Association with the Cruthin therefore places the roots of the tribe in north-east Ireland, which is compatible with other accounts that state their origin as being on the shores of Lough Neagh.
If so, Fochae (Foicheadh, Fochadh) Beg (Gaelic for 'small') from whom some sources have the Corca Oiche of Munster descending[17] along with his six sons: Fiodhach, Oineann, Cronan, Caiseadha, Baithe and Iinge.,[18] could also be associated with Fergus Foga or his mother.
[20][21] Further reinforcing the tribe's connection with Ailill Flann Bec, his grandson Conal Corc is also mentioned as having been fostered by a witch, Fidelm (possibly also known as Lair Derg), daughter of Moethaire son of Clithaire of the Corca Oíche.
[22] By the 6th century the Corca Oíche appear to have moved further west and allied themselves, at least for a time, with the Ciarraige Luachra, a tribe that occupied parts of present-day County Kerry.
Saint Molua, born of the Corca Oíche, founded a monastery in Killaloe in the heart of Dalcassian territory, therefore it is likely the two tribes were well aware of one another and possibly on friendly terms.
One source suggests that at the time of Saint Ita, they dwelled "on the banks of the Maigue" and refers to their chieftain as carrying the surname O'Macassy.
[26] The name of this territory arises on several occasions during the Norman period through to the 16th century with slightly different spellings, all most likely corruptions of Tuath Corca Oíche.
The historian Giolla na Naomh Ua hUidhrín (O'Heerin) who died in 1420, noted 'Macassa' among the principle families of the "Chonall" (probably the Ui Chonaill Gabhra) alongside Collins, Mulholland, MacEniry, O’Bilraidhe, and O’Bearga, and wrote the following poem: "Corco Oiche of the delightful woods, The country of white mantles and clear streams, A fair land of great fertility, Is governed by O'Maolmackessy.
"[29] Further evidence of the Corca Oiche presence in this area is the township of Ballymackesy (Baile Uí Mhacasa), situated only a few kilometres south of Newcastle West.