Proper noun
the Earl of Cork
(Ireland, slang, obsolete, card games) The ace of diamonds.
He ascended to the Irish Peerage as Lord Boyle, Baron of Youghal, 6 September 1616, and was created Earl of Cork and Viscount Dungarvan, 26 October 1620. Source: Internet
Oliver Cromwell is reported to have said of Richard Boyle 'If there had been an Earl of Cork in every province it would have been impossible for the Irish to have raised a rebellion.' Source: Internet