[6][7] The meaning " It is also known as Mac Murchadha Caomhánach (an example of an Irish agnomen; see Ó Catharnaigh Sionnach or Fox of Fir Teathbha), but is often now rendered 'Caomhánach'.

[8] The surname was first assumed by Domhnall Caomhánach (the eldest son of the 12th-century king of Leinster, Diarmait Mac Murchada) in Ireland.

[9] A considerable number of anglicised variations of Caomhánach exist, with some of the most common being: "Kavanagh", "Cavanagh", "Kavanaugh" and "Cavanaugh".

[14] The surname was possibly adopted by Síl Fáelchán clansmen in preference to the earlier name MacMurrough, given the prestige associated with the dynamic junior line that seized the chiefship of the Uí Cheinnselaig tribal group in the High Middle Ages.

According to historian C. Thomas Cairney, the Kavanaghs were one of the chiefly families of the Uí Ceinnselaig who in turn were a tribe from the Dumnonii or Laigin who were the third wave of Celts to settle in Ireland during the first century BC.