Thieves who carry about pins, laces, and other pedlars wares, and under the pretence of offering their goods to sale, rob houses, or pilfer any thing they can lay hold of.
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.
Irish Legs * IronNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes