Ormon or Ormand is a very old surname and can vary in spelling in old texts. However the spelling, Ormond, without an e is specific to the earldom, while Ormonde with an e is specific to the dukedom. (Jane Fenlon, ‘The decorative plasterwork at Ormond castle: a unique survival’, Architectural History, 41 (1998), 67-81, at 80).