O'Cathasaigh is an Irish surname that translates to "descendant of Cathasach," with "Cathasach" meaning "vigilant" or "watchful." This name is associated with several notable families in Ireland, particularly in the province of Connacht. The O'Cathasaigh clan has historical ties to the region, contributing to local culture and heritage. The surname is often anglicized as O'Casey or Casey. Families bearing this name have been involved in various professions, including politics, literature, and the arts. The O'Cathasaigh lineage reflects the rich tapestry of Irish history and the significance of surnames in tracing ancestry.