Green’s Dictionary of Slang

money; a payment.

1812		Vaux Vocab. of the Flash Lang.
1822		Tom And Jerry; Musical Extravaganza I vii: I know not whether more wamly to admire your astonishing judgment, or the spirit with which you fork out the dimmock.
1834		(con. 1737–9) W.H. Ainsworth Rookwood (1857) 249: I have pocketed the dimmock.
1844		New Sprees of London 20: The passport dimmock, is a brown broad, which goes to the concert cad, or conductor, the piano-torturer being tipped by the great boss of the concern.
1848		Flash Dict. in Sinks of London Laid Open.
1855		Yokel’s Preceptor 30: Dimmock, Money.
1864, 1867, 1870		Hotten Sl. Dict.
1871–82		B.M. Carew Life and Adventures.
1882		Sydney Sl. Dict. (2 edn) 3: Dimmock - Money; from the U.S. dime (10 cts.).