Complex sentence: The name is an anglicisation of the Irish language surnames "Ó Muiris", "de Muiris", "Mac Muiris" (Fitzmaurice/Morrison) and "Ó Muireasa" (Morrissey).
Split into simpler sentences: The name is an anglicisation of the Irish language surnames "Ó Muiris" and "de Muiris". Related surnames include Fitzmaurice, Morrison "Mac Muiris" and "Ó Muireasa" (Morrissey).