(A popular title for) James Scott, Duke of Monmouth and Buccleuch (1649–85), distinguishing him from the Duke of York, his Roman Catholic uncle (later James II).
Origin
Late 17th century.
Definition of Protestant Duke in US English:
Protestant Duke
noun
(A popular title for) James Scott, Duke of Monmouth and Buccleuch (1649–85), distinguishing him from the Duke of York, his Roman Catholic uncle (later James II).