Deegan is an Irish surname, anglicized from Ó Duibhginn, built from dubh, black, and ceann, head, so it means "dark-haired" or "black-headed". It joined the American boom in Irish surname names along with Keegan and Teagan. In the United States Deegan entered the top 1000 in 2008, peaked at number 835 in 2011 and has since eased to number 2024 in 2025.