The quantity of tobacco put into the mouth at one time. To quid tobacco; to chew tobacco. Quid est hoc? hoc est quid; a guinea. Half a quid; half a guinea. The swell tipped me fifty quid for the prad; the gentleman gave fifty pounds for the horse.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Quick and Nimble * QuidsNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes