Nun vs Hooker

Hey there, author! Explain Bear is here because your brain is smoother than a freshly waxed bowling ball. This joke is simple wordplay, combining a setup about two drastically different professions (a nun, representing piety and trust, and a hooker, representing paid sex). The punchline relies on the similar sound of "trust" and "thrust" (a euphemism for the sexual act) to deliver a quick, crude laugh. You must be really dumb if you need this explained.