Green’s Dictionary of Slang

body of divinity bound in black calf n.

a parson.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Body of Divinity, bound in black calf a Parson.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn).
1811		Lex. Balatronicum.
1821		R. Waln Hermit in Philadelphia (2 ser.) 26: ‘He looks like a Body of Divinity bound in black calf;’ continued a third. — (The absentee was dressed in a full suit of mourning).
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.