MEANING

 

The phrase (if you’ll) excuse (or pardon) my French is used as an apology for swearing.

 

ORIGIN

 

The current sense seems to derive from an actual apology for speaking French. (It is therefore unnecessary to invoke the centuries-old adversarial relationship between the English and the French.) The form pardon my French is first attested in Randolph, a Novel (1823), by the American writer and critic John Neal (1793-1876):

I have read this work [Julie, or the New Heloise] of the “Divine Rousseau,” as he has been called […]. And the result is not, what he so pleasantly predicted in his preface. I do not believe that I am yet, “une fille perdue [= a lost girl]!” Pardon my French.

And the form excuse my French is first recorded in The Button-holder, a story by Baron Karl von Miltie published in The Lady’s Magazine (London) of November and December 1830. (This story was republished in 1831 as part of the book The Twelve Nights.):

My dear Mr. Heartwell, you are come to see me at last. Bless me, how fat you are grown!—absolutely as round as a ball:—you will soon be as embonpoint (excuse my French) as your poor dear father, the major.

(As an adjective, embonpoint means plump, as a noun, plumpness; it is a borrowing from the French noun embonpoint, which nowadays translates negatively as corpulence, from the phrase en bon point, which had the positive sense in good condition, in good health.)

In Two Lives: or, To seem and to be (1846), by the American author Maria Jane McIntosh (1803-78), a French noble, the Marquis de Villeneuve, says pardon my French to an American lady who can speak French, as an apology for using French euphemistically:

The American ladies are charming, very charming, mais un peu prudes [= but a little prudish]. Pardon my French: I could not be so bold to say it in English.

The first known use of the phrase that does not refer to French is in Marian Rooke; or, The Quest for fortune (1865), by the American writer Henry Sedley (1835-99). On taking leave of his host, Hugh Gifford, the very rude Mr Doke says:

All right. No harm done, anyhow. I heard you had some leanin’s towards public life, and that bein’ in my line I just thought I’d call. Dreadful good brandy o’ yourn. Ha! ha! ha! My respecks. Excuse my French.

The meaning of the phrase is clearer in A Waterlogged Town, an 1895 short story by the American author, artist and engineer Francis Hopkinson Smith (1838-1915):

“I don’t mind saying,” and a wicked, vindictive look filled his eyes, “that of all the cussed holes I ever got into in my life, this here Venice takes ― the ― cake. […]
“Do not the palaces interest you?” I asked inquiringly, in my effort to broaden his views.
“Palaces be durned!  Excuse my French. Palaces! A lot of cave-in old rookeries; with everybody living on the second floor because the first one’s so damp ye’d get your die-and-never-get-over-it if you lived in the basement, and the top floors so leaky that you go to bed under an umbrella; and they all braced up with iron clamps to keep ’em from falling into the canal, and not a square inch on any one of ’em clean enough to dry a shirt on!