When blessing his public audience during the weekly Vatican blessing that takes place every Sunday, he wanted to say caso, which means "example" or "case."
Sadly enough, the pope pronounced it as cazzo. This four-letter word is the Italian equivalent of f*ck, c*ck or d*ck.
According to Italian newspaper The Local, the Pope said the following to his audience in St Peter’s Square:
“If each one of us does not amass riches only for oneself, but half for the service of others, in this f*ck [pause], in this case, the providence of God will become visible through this gesture of solidarity.”
According to The Daily Mail, the mistake is a common one among non-native Italian speakers. Francis, whose blessing was aimed at the current crisis in the Ukraine, quickly realized his mistake and corrected himself.
However, the moment will be remembered forever. The error only added to his image as the "people's pope”.
To listen to Il Papa's historic slip of the tongue, watch the video below.