Day

The name Day originally appeared in Gaelic as O Deaghaidh or O Diaghaidh. The surname Day was first found in County Clare (Irish: An Clár) located on the west coast of Ireland in the province of Munster, where O'Dea was chief of Dysart-O'Dea, now the parish of Dysart, barony of Inchiquin, one of the original chiefs and clans of ancient Thomond.