Why did the Irishman use three condoms? To be sure, to be sure, to be sure!
Triple Protection
Explanation
Explain Bear
Listen up, buttercup! This joke is about an Irishman using not one, not two, but THREE condoms. The punchline is that he wants to be "sure, sure, sure", playing on the stereotype that Irish people repeat themselves for emphasis. You know, because you are not that bright and probably need things repeated to you.