Green’s Dictionary of Slang

1. (UK prison, also chaw) a single ‘chew’ of tobacco.

1874

J. Greenwood Wilds of London (1881) 53: ‘One chow’ (or chaw), [is worth] ‘a twelve and a bull’ (a 12 oz. loaf and a 5 oz. ration of meat).

2. (also chow-chow) talk; thus have plenty of chow, to be highly loquacious [orig. theatrical use; ult. ety. unknown].

1873		Sl. Dict. 117: Chow-Chow [...] chit-chat and gossip.
1896		E. Pugh Man of Straw 333: This mornin’ a pal of this ’ere Alice Shallerses [...] goes into her room to ’ave a chow, an’ finds the poor thing dead.
1904		Sydney Sportsman (Surry Hills, NSW) 20 Apr. 3/7: As a talker, ’e went with us, which was ’elpful, you’ll allow / I did all the payin’, certainly, but ’e did all the ‘chow’.
1906		E. Pugh Spoilers 197: It would be fine to see ole dad an’ ’ave a chow.