Woulfe treats Ó Fiacháin (Feehan, Fehane) and Ó Feichín (Feeheen, Feen) as Connacht variants, but the latter is in fact distinct, being the name of a small west Cork sept. Fegan has been recorded as a synonym of Fehan, but in fact Fegan is basically a different name: it, Ó Faodagáin, is numerous in the Oriel country-Louth, Armagh etc.-(see Irish Families, p. 137). Feehan has for many centuries been associated with the Ormond country, particularly Cos. Tipperary and Kilkenny. The early anglicized spelling of Irish surnames as set down in legal records is very corrupt and may be misleading.

Probably Muirihirt and Thomas O'Fechan, who appeared before a court held in Clonmel in 1295 were of this sept; as no doubt was Philip MacShoan O'Fethan who was convicted of robbery in Co. Tipperary in 1359,while another, equally picturesquely named, Conghor Leith O'Fean, was fined at Clonmel in 1380. By 1601 the name had assumed a form nearer to the modern Feehan: in that year Teige MacNicholas O'Fehin was one of a number of men belonging to the Ormond territory who were granted “pardons”, i.e. immunity from the current anti-Irish legislation. Coming to modern times, there were 57.householders of the name in Co. Tipperary in 1855 and birth registrations of the 1860s indicate that Feehan was then found mainly in the Munster—Kilkenny area to which they traditionally belong —— only 3 of the 22 births registered in an average test year were outside it and those were in or near Co. Louth. A generation later the same source shows the name in all the provinces, less than half being recorded in the O'Feehan homeland and the majority of the rest being in Co. Louth. As a rule names closely identified with a locality continue to be mainly found there always, and it therefore appears probable that Feehan has sometimes been substituted for Fegan in Co. Louth.