Fig.: please excuse my rude and vulgar language

Pardon my French, but this time I'm fucking pissed off

Scusate il linguaggio, ma questa volta sono veramente incazzato

Excuse my French, but that guy is a real son of a bitch!

Scusate il linguaggio, ma quel tale è un gran figlio di puttana!

Sources suggest that this phrase, dating from the early 20th century, originated as a literal excuse for using a French phrase in conversation with someone who didn't speak the language. Today, it's used, as a sort of mild excuse, right before or right after saying a "dirty" word