Ceallaigh, Ceallach, Ó Ceallaigh, Ó Caollaidhe, Ó Caollaighe, Ó Cadhla, Mac Caochlaoich: “war or contention”.
Kelly, Kelley, O’Kelly, Kealy, Keely, Keily, Kehelly, Kehilly, Coakley.
Kelly is the second most common surname in Ireland and originates from at least seven different and unrelated ancient clans or septs. These include O’Kelly septs from Meath, Derry, Antrim, Laois, Sligo, Wicklow, Kilkenny, Tipperary, Galway and Roscommon, and the McKelly sept from East Connaught.
One of the major septs is the O’Kellys of Ui Maine, or Hy Many, a territory in East Galway and South Roscommon. O’Kelly derives from the Gaelic O Ceallaigh, meaning “descended from Ceallach.” Ceallach was the son of Finnachta, a chief of the Hy Many people around A.D. 874.
Here’s a list of various clan websites:
Kelly may also mean ‘bright-haired’ or ‘troublesome’ – you choose! :-)