Green’s Dictionary of Slang

a farthing; in pl., money, cash.

1656–7		Burton’s Diary (1828) I 335: The poor man [...] sent to one Mr. Best, in London, to pay her 40l. to accommodate her for her journey home; but she having received the griggs set sail another way .
c.1698		B.E. Dict. Canting Crew n.p.: Not a Grig did he tip me, not a Farthing wou’d he give me.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) 206: Grig, a farthing. Not a grig did he tip me, i.e., not a farthing would he give 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.
1811		Lex. Balatronicum.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.
1839		(con. 1703) W.H. Ainsworth Jack Sheppard (1840) 34: He shall go through the whole course [...] unless he comes down to the last grig.
1857		‘Ducange Anglicus’ Vulgar Tongue.
1881		Morn. Bulletin (Rockhampton, Qld) 18 July 2/6: A ‘fiddler’ is used for a farthing as well as a sixpence, and the same explanation does for both. ‘Gig’ is a corruption of the word ‘Grig,’ and ‘Grig’ itself is a slang word for a merry little fellow.
1937		Nott. Eve. Post 30 Apr. 6/3: Now we come to the humble farthing [...] it was soon turned into rhyming slang into ‘Covent Garden’. Other names are ‘quartareen’ [...] ‘fadge,’ ‘grig,’ and ‘fiddler’.