To stop. To finish. To end. The cove tipped the prosecutor fifty quid to stash the business; he gave the prosecutor fifty guineas to stop the prosecution.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Star Lag * StateNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes