Green’s Dictionary of Slang

well-off, wealthy.

1688		T. Shadwell Squire of Alsatia I i: Thou shalt be rhinocerical, my lad, thou shalt.
c.1698		B.E. Dict. Canting Crew n.p.: Rhinoceral c. full of Money. The Cull is Rhinoceral, c. the Fop is full of Money.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1834		(con. 1737–9) W.H. Ainsworth Rookwood (1857) 187: Your old dad, Sir Piers (God help him!), had the gingerbread, that I know; he was, as we say, a regular rhino-cerical cull.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 199: RHINOCERAL, rich, wealthy, abounding in rhino.
1873		Sl. Dict.