Excuse my French
This phrase is used in conversation when someone swears or curses, and is a request for forgiveness for using taboo language.
Of course, both the speaker and the listener are very much aware that whatever was said was in English and not French.
The expression originates from the 19th century, and was used literally.
When English people used French expressions in conversation, they would often apologise for it, presumably because many of their listeners were not familiar with the language!
Example: "Excuse my French, but that guys needs a kick in the ass!"
