Ó Flannagáin is an Irish surname that translates to "descendant of Flannagán." The name is derived from the personal name Flann, which means "red" or "ruddy" in Old Irish. This surname is primarily associated with families from County Kerry and County Clare in Ireland. The Ó Flannagáin family has historical significance, often linked to the Gaelic nobility. They were known for their contributions to Irish culture and history, particularly during the medieval period. The name is part of a broader tradition of Gaelic surnames that reflect lineage and ancestry in Ireland.