earl of Cork, n.¹ — Green’s Dictionary of Slang

earl of Cork n.¹

[‘the worst ace and the poorest card in the pack’, so called from the contemporary earl, who was the poorest nobleman in Ireland]

(Anglo-Irish) the ace of diamonds.

1830		W. Carleton Traits and Stories of the Irish Peasantry n.p.: ‘What do you mean by the Earl of Cork?’ asked Mr. Squander. ‘The ace of diamonds, your honour. It’s the worst ace, and the poorest card in the pack, and is called the Earl of Cork, because he’s the poorest nobleman in Ireland.’.
1851		Durham Co. Advertiser 14 Nov. 2/1: Popular names for certain Playing Cards [...] Ace of Diamonds...The Earl of Cork.
1864, 1867, 1870		Hotten Sl. Dict.
1895		Crowe Aus. Sl. Dict. 26: Earl of York [sic], the ace of diamonds.
1898		Princeton Union (MN) 20 Jan. 7/6: In Ireland the ace of diamonds is nicknamed the ‘Earl of Cork’ because they say it is the worst ace and the poorest card in the deck.
1908		Bucks Herald 4 Jan. 7/3: In Ireland it [i.e. the ace of diamonds] is called ‘The Earl of Cork’.
1935		A.J. Pollock Und. Speaks 35/1: Earl of Cork, ace of diamonds.
1997		Share Slanguage.