Green’s Dictionary of Slang

an Englishman.

1855		Southern Sentinel (Plaquemine, LA) 18 Aug. 1/4: Oh, thjat ‘Bono Johnny’ had abandoned Silistria, and our enemy had never been taught the value of mud in that sanguinary siege.
1865		Sydney Morn. Herald 21 Feb. 2/2: ‘Bono Johnny,’ I add as an explanatory clincher. [...] The phrase seemed then to be a universal hermeneutic.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1909		J. Ware Passing Eng. of the Victorian Era 41/2: Bono Johnny (Pigeon Chinese). A good fellow. A Chinese invention; used by English sailors as warrant of good intentions.