Green’s Dictionary of Slang

a farthing.

1859, 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: 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.