Title: Pardon my French
Content:  "Pardon my French" or "Excuse my French" is a common English language phrase ostensibly disguising profanity as words from the French language. The phrase is uttered in an attempt to excuse the user of profanity, swearing, or curses in the presence of those offended by it, under the pretense of the words being part of a foreign language.
Title: Pardon my French
Content:  At least one source suggests that the phrase "derives from a literal usage of the exclamation. In the 19th century, when English people used French expressions in conversation they often apologized for it – presumably because many of their listeners (then as now) wouldn't be familiar with the language". The definition cites an example from The Lady's Magazine, 1830: "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." The phrase has been used in broadcast television and family films where less offensive words are preceded by "pardon my French" to intensify their effect without violating censorship or rating guidelines. An example is in the movie Ferris Bueller's Day Off; Cameron Frye says, "Pardon my French, but you’re an asshole" on a phone call with the Edward Rooney.
Title: Excuse My French (2006 TV series)
Content:  Excuse My French is an RDF language programme on the BBC where three celebrities with varying levels of French had one month to learn enough of the language to be able to carry out a task related to their area of expertise in French. They did this while staying in a villa in Provence. They were helped by three teachers (Thierry, Patricia and Christine) from the Institut Français. The series was screened on BBC Two on Tuesday evenings at 9pm in July and August 2006, and consisted of four episodes. It featured Esther Rantzen, Marcus Brigstocke and Ron Atkinson. Rantzen had the best knowledge of French of the three 
Title: Glossary of French expressions in English
Content:  to assist in remembrance, or a diplomatic paper proposing the major points of discussion ; amour propre: "Self-love", Self-respect. ; amuse-bouche or amuse-gueule: lit. "mouth-amuser"; a single, bite-sized hors d'œuvre. In France, the exact expression used is amuse-gueule, gueule being slang for mouth (gueule is the mouth of a carnivorous animal; when used to describe the mouth of a human, it is vulgar—akin to "gob"— although the expression in itself is not vulgar). The expression refers to a small mouthful of food, served at the discretion of the chef before a meal as an hors d'oeuvre or between main courses. ; ancien 
Title: Glossary of French expressions in English
Content:  with a military force. ; esprit de l'escalier: lit. "wit of the stairs"; a concise, clever statement you think of too late, that is, on the stairs leaving the scene. The expression was created by French philosopher Denis Diderot. ; l'État, c'est moi!: lit. "I am the state!" — attributed to the archetypal absolute monarch, Louis XIV of France. ; étude: a musical composition designed to provide practice in a particular technical skill in the performance of an instrument. French for "study." ; étui: small ornamental case for needles or cosmetics. ; excusez-moi: "Excuse me". ; extraordinaire: extraordinary, usually as a following adjective, as "musician extraordinaire."  
Title: Excuse My French (1974 TV series)
Content:  Excuse My French was a Canadian television sitcom, which aired on CTV from 1974 to 1976. Produced by CFCF-TV's Champlain Productions division, the series starred Stuart Gillard and Lisa Charbonneau as Peter and Marie-Louise Hutchins, a mixed anglophone-francophone couple living in Montreal and fighting the disapproval of their families. The cast also included Earl Pennington as Peter's wealthy publisher father Charles, Paul Berval and Pierrette Beaudoin as Marie-Louise's parents Gaston and Thérèse Sauvé, and Daniel Gadouas as Marie-Louise's Quebec separatist brother Jean-Guy. The series, produced in Montreal, was judged the best television show of the year by the Montreal branch of the Association of Canadian Television and Radio Artists in 1975. Although popular in the ratings and with critics, the series ended in 1976 when Gillard moved to the United States to work as a writer for The Sonny & Cher Show.
Title: Glossary of French expressions in English
Content: Quai d'Orsay: address of the French foreign ministry in Paris, used to refer to the ministry itself. ; Quatorze juillet: "14th of July", usually called Bastille Day in English. The beginning of the French Revolution in 1789; used to refer to the Revolution itself and its ideals. It is the French National Day. ; quelle bonne idée!: What a good idea! ; quel dommage!: What a sad thing! (can be used sarcastically). ; quelle horreur!: What a horrible thing! (can be used sarcastically). ; quelle surprise!: What a surprising thing! (mostly used sarcastically) 
Title: Glossary of French expressions in English
Content:  du mal" instead of "qui mal y pense"). The sentence Honni soit qui mal y pense (often with double n) can stil be used in French as a frozen expression to mean "Let nobody think ill of this" by allusion to the Garter's moto. A more colloquial quasi-synonymous expression in French would be en tout bien tout honneur. ; hors de combat: lit. "out of the fight": prevented from fighting or participating in some event, usually by injury. ; hors concours: lit. "out of competition": not to be judged with others because of the superiority of the work to the others. ; hors d'œuvre: lit. "outside the [main] work": appetizer.  
Title: Glossary of French expressions in English
Content:  in French also the word for crescent. ; cul-de-sac: originally "bottom of sack" and used in English in anatomy since 1738. Used for dead end (street) since 1800 in English, since 14th century in French. The often heard erroneous folk etymology "arse [buttocks] of the sack" is based on the current meaning of cul in French, but cul-de-sac is used to refer to dead ends in modern French and is not vulgar, though the terms impasse and voie sans issue are more common in modern French.    c'est la guerre: "That's war!", or... c'est la vie: "That's life!" or "Such is life!"    
Title: Glossary of French expressions in English
Content:  to an English speaker. They are most common in written English, where they retain French diacritics and are usually printed in italics. In spoken English, at least some attempt is generally made to pronounce them as they would sound in French; an entirely English pronunciation is regarded as a solecism. Some of them were never "good French", in the sense of being grammatical, idiomatic French usage. Some others were once normal French but have become very old-fashioned, or have acquired different meanings and connotations in the original language, to the extent that they would not be understood (either at all, or in the intended sense) by a native French speaker.

Question: where does the expression excuse my french come from?
Answer: English Literature.