Before one could say Jack Robinson; a saying to express a very short time, originating from a very volatile gentleman of that appellation, who would call on his neighbours, and be gone before his name could be announced.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Jack Pudding * Jack SpratNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes