Etymology: Since the Elizabethan era, the word "nun" has been slang for a prostitute, likely due to anti-Catholic sentiment engendered by Protestant reformers outraged by the corruption of the Medieval church. (Modern reference: William Faulkner, "Requiem for a Nun"). A nunnery referred to a brothel.
See also: Abbess, Bordello, Brothel, Crib, Humpty dump, Nunnery, Whorehouse]
Tobias St, Lazare, "Who Will Walk With William? Shakespeare for Students?" (Cambridge Univ. Press, 1967)
Sam: "Go away you Nun."
2)Sam: "Oi, Daniel, pass the pepper corns."
*Daniel drops the pepper corns*
Sam: "Oh you prick, I wanted to eat those pepper corns, your such a Nun."
Daniel: "Don't be so mean, it was an accident."
3) Townie in the street: "I fucked yo mama!"
Sam: "Your mum's a Nun."