A butcher’s boy of St. Patrick’s Market, Dublin, or other Irish blackguard; among whom the exclamation, or oath, by the Holy Father (meaning the Pope), is common.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Holiday * Holy LambNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes