A thin shoe. To pump; to endeavour to draw a secret from any one without his perceiving it. Your pump is good, but your sucker is dry; said by one to a person who is attempting to pump him. Pumping was also a punishment for bailiffs who attempted to act in privileged places, such as the Mint, Temple, &c. It is also a piece of discipline administered to a pickpocket caught in the fact, when there is no pond at hand. To pump ship; to make water, and sometimes to vomit. Sea phrase.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Pull * Pump WaterNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes