O’Suilleabhain: “one-eyed” or “hawk-eyed”.
The O’Sullivan clan is an ancient family that emerged as the ruling class of a small, wandering tribe of warrior Celts now called the ‘Gaels’. It is thought that the tribe originated in the Fertile Crescent, immigrated to the steppes of the Caucasus Mountains, fought and pillaged its way across southern Europe, and finally settled in its own ‘promised land’, the island of Eire.
It is also generally understood that the O’Sullivan clan represents the most senior bloodline of the Gaelic families. The senior tribe, and royal family, of the Gaelic Celts in Ireland was known as the Eoghanacht, the descendants of Eoghan, and the most senior branch of the Eoghanacht was in fact the O’Sullivan clan.