Green’s Dictionary of Slang

(UK Und.) a horse.

1781		G. Parker View of Society II 50: He has gotten an old Grogham worth about five pounds.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1821		‘An Amateur’ Real Life in London I 248: When did you sell your Daisy-kicker or Grogham?—for these terms are made use of among themselves as cant for a horse.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.
1859		Matsell Vocabulum.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn).
1864, 1867, 1870		Hotten Sl. Dict.