Originally recorded in many spellings including Mac Scanlon, O' Scanlon, O' Scannill, O' Scanlan, but now more usually as Scanlon, and more rarely Scannell, Scanlan, Scanlin, and possibly others, this is an ancient Irish surname. It derives from the Gaelic pre 10th century personal 'Scanlain' which translates literally as 'The contentious one'. There were originally three quite distinct septs or clans, the first having the prefix 'Mac' and they held territory in County Louth and gave their name to Ballymascanlon near Dundalk. The second belonged to West Munster and specifically the Counties of Cork, Kerry, Limerick, and Clare, with Ballyscanlan in County Clare deriving its name from the sept. A third branch settled in County Sligo and appears as O' Scannell and O' Scanlon in the 'Composition Book of Connacht' in 1585. The first recorded spelling of the family name is shown to be that of Most Reverend Patrick O' Scanlan (also called O' Scannell),and dated 1262 - 1272, when he was Bishop of Raphoe and afterwards of Armagh. Surnames became necessary when governments introduced personal taxation. In England this was often known as the Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.