Keenan (Cianán) is a male Irish name which means "ancient, distant". Keenan is an Anglicisation of the Irish name Cianán which is a diminutive of Cian. The Ó Cianáin clan (Keenan) were the traditional historians to the McGuire clan.
Recorded as O'Keenan and more usually Keenan, this is an Irish surname. Found mainly in the Ulster and northern counties of Fermanagh and Monaghan, it originates from the ancient pre 10th century Gaelic name O' Cianain 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.
According to the United States' Social Security Administration, Keenan was the 607th most popular first name for newborns in the United States in 2006, which is a decrease from being the 362nd most popular in 1992.