Originally a Scottish name, representing an Anglicized spelling of the Gaelic nickname Ruadh ‘red’. It has since spread to other parts of the English-speaking world, where it is often reanalysed as Old French roy ‘king’ (compare Leroy).
Irish (Munster): reduced Anglicized form of Gaelic Ó Luanaigh ‘descendant of Luanach’, a personal name derived from luan ‘warrior’. Compare Lane 3 and Lamb 3. Woulfe distinguishes the Munster name Ó Luanaigh from the Ulster name Ó Luinigh, whence Lunney.However, many of the Anglicizations are the same.