Irish (English?) sense of humour

‘Mary goes to England in rags and comes back a year later in fine clothes and throwing away money right and left. Meets Father O’Byrne who says: “Tell me, Mary,. How did you get all that money?”
‘Says Mary, shamefaced: “Oi became a prostitute, Father.”
‘”What’ that you say?” cries Father O’Byrne in a fury.
‘”Oi became a prostitute, Father,” says Mary again.
‘”Ah, sure that’s all roight,” says Father O’Byrne with a sight of relief. “Oi was after thinking you said you’d become a Protestant!”’
(J.G. Farrell, Troubles, p. 392)