"Excuse my French"

For "Excuse my French", Phrase Finder gives the definition as the origin. Has anyone an idea of the actual origin?

Meaning
Please forgive my swearing.

Origin

A coy phrase where someone who has used a swearword attempts to pass it off as french.

Thanks

m.

I think this goes back to an age-old rivalry between France and the UK.
In the UK, anything considered a bit risque or off-color was considered to be of French origin.
For instance: "French kiss" "French tickler" etc.
So if someone used a swear word then they would attribute that word to the French as in "Excuse my French, but what the f**k happened to that report I was supposed to have this morning??".
Can anybody east of NY confirm this?

Replies