Keenan is an Irish surname meaning 'ancient, distant' in the Irish language. It is derived from Ó Cianáin 'descendant of Cianán' (a diminutive of Cian). The Ó Cianáin clan were hereditary historians to the Mac Uidhir.[1]
Recorded as O'Keenan and more usually Keenan, this is an Irish surname. Found mainly in Ulster counties Fermanagh and Monaghan, it originates from the ancient pre-10th-century Gaelic name Ó Cianáin meaning "The descendant of the faithful one" or similar. It may not have been entirely coincidence that the clan was famous throughout the Medieval Period for producing both high-ranking members of the church, and early historians, in several cases the same thing. The first recorded scribe was Adam O' Caianain, who was also the canon of Lisgool in Fermanagh. He is mentioned in the annals known as the "Four Masters" as being the historian to the famous Maguires of County Fermanagh. It is said that in 1659 in Petty's Census of Ireland that the spelling was found as MacKeenan, but if so this spelling is now completely extinct and research suggests that the original recording may have been a clerical mistake.
