A justice of peace, or magistrate. Also a judge or chairman who presides in court. I clapp’d my peepers full of tears, and so the old beak set me free; I began to weep, and the judge set me free.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Bayard of Ten Toes * BeanNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes