O'Cathail is an Irish surname that originates from the Gaelic name Ó Cathail, meaning "descendant of Cathal." The name Cathal itself translates to "battle ruler" or "strong in battle," reflecting a historical significance in Irish culture. Families with this surname are primarily found in Ireland, particularly in the provinces of Connacht and Ulster. The O'Cathail family has a rich heritage, often associated with various clans and historical figures in Irish history. Like many Irish surnames, it has variations in spelling, including O'Kahill and O'Callaghan. The name is part of the broader tapestry of Irish genealogy, representing the legacy of the Gaelic language and culture.