Green’s Dictionary of Slang

1. a sixpence.

c.1698		B.E. Dict. Canting Crew n.p.: Simon c. Six-pence.
1703		Hell Upon Earth 6: Simon, Six-pence.
1708		J. Hall Memoirs (1714) 13: Simon, Six-pence.
1721		Cibber Refusal 9: I owe Crop the Lender a Brace, and if I have a single Simon to pay him, rot me.
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.
1795		Sporting Mag. June VI 171/2: Wou’d I wear out my stump of a leg; / For a Simon.
1811		Lex. Balatronicum.
1820		Jack Randall’s Diary 65: For me no more shall hogs or simons ring.
1836–7		Dickens Pickwick Papers (1999) 599: He must be the representative of the united parishes of Saint Simon Without and saint Walker Within.
1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.
1881		Morn. Bulletin (Rockhampton, Qld) 18 July 2/6: For our next coin in value [i.e. sixpence] twenty names are found [...] ‘Fyebuck,’ ‘half-hog,’ ‘kick,’ ‘lord of the manor,’ ‘pig,’ ‘pot,’ ‘say saltee,' ’sprat,’ ‘snid,’ ‘simon,’ ‘sow's baby,’ ’tanner,’ tester,’ and ‘tizzy’.
1885		Household Words 20 June 155: The old joke... about St. Peter’s banking transaction, when he ‘lodged with one Simon a tanner.’ And this reminds us that simon is also a slang term for a sixpence, and may possibly owe its origin to this play upon the other word [F&H].

2. (US) $1.

1859

Harper’s Mag. Sept. 572/2: I was first in say, and bet a Simon [DA].