To save his groats; to come off handsomely: at the universities, nine groats are deposited in the hands of an academic officer, by every person standing for a degree; which if the depositor obtains with honour, the groats are returned to him.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
To Grind * GrogNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes