Green’s Dictionary of Slang

1. a nickname for an Irishman.

c.1869

‘Irish Church Question’ in C. Hindley Curiosities of Street Lit. (1871) 84: Noble Gladstone, the Liberator of the Land of Donovans.

2. a potato.

1835		G. Kent Modern Flash Dict.
1840		Flash Mirror 19: All sorts o’ vegetables, such as donovans, cabbage, carrots, &c.
1866		‘Irish Church Question’ in C. Hindley Curiosities of Street Lit. (1871) 84: And the land of donovans and buttermilk shouted, No surrender.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1989		H. Rawson Dict. of Invective (1991) 210: For reasons that should not seem terribly obscure, the Irish potato also has been known as a bog orange, Donovan, Mick, or murphy.
1997		Share Slanguage.