Green’s Dictionary of Slang

a donkey, also attrib.

[1784		H. Lemoine ‘The Clever Fellow’ in Wit’s Mag. 155/1: A saucy rolling blade am I, / I keep a Donkee Dick].
1811		Lex. Balatronicum n.p.: Dickey. An ass. Roll your dickey; drive your ass.
a.1823		R. Bloomfield Richard and Kate n.p.: Amongst the leaders ’twas decreed Time to begin the Dickey Races, More famed for laughter than for speed [F&H].
1838		‘Paul Pry’ Oddities of London Life II 268: ‘As for hurting my dickey,’ said the man, ‘by lettin him fall, the gemman's werry much mistaken’.
1841		J. Mills Old Eng. Gentleman (1847) 89: A young dickey, in the full kick of youth, mistook some sweet briar for a thistle.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn).
1864, 1867, 1870		Hotten Sl. Dict.
1890–1904		Farmer & Henley Sl. and Its Analogues.