O'Caomhanaigh is an Irish surname that originates from the Gaelic name Ó Caomhanaigh, meaning "descendant of Caomhán." The name is associated with the ancient Irish nobility and is primarily found in the province of Connacht, particularly in County Galway. The O'Caomhanaigh family has historical ties to the region, often linked to the O'Flahertys, a prominent Gaelic clan. Over time, the name has evolved in spelling and pronunciation, with variations such as Cahoon and Cavanagh appearing in different regions.