When I swear in English I attempt to pardon it by saying "excuse my French" Where did this saying come from?

I'm guessing that they were pioneers in using profanity in public.

1) "pardon (n.)
c.1290, "papal indulgence," from O.Fr. pardonner "to grant, forgive," from V.L. *perdonare "to give wholeheartedly, to remit," from L. per- "through, thoroughly" + donare "give, present" (see donation). Meaning "passing over an offense without punishment is from c.1300; strictly legal sense is from 1328, in Anglo-Fr. Weaker sense of "excuse for a minor fault" is attested from 1548. The verb is first recorded c.1430.
" 'I grant you pardon,' said Louis XV to Charolais, who, to divert himself, had just killed a man; 'but I also pardon whoever will kill you.' " [de Sade]
Pardon my French as exclamation of apology for obscene language is from 1895. A pardoner (1362) was a man licensed to sell papal pardons or indulgences.
French
O.E. frencisc "of the Franks" (see frank). Euphemistic meaning "bad language" (pardon my French) is from 1895. Used in many combination-words, often dealing with food or sex. French fries is 1918 Amer.Eng., from French fried potatoes (1894, first attested in O.Henry); French dressing first recorded 1900; French toast is from 1660. French letter "condom" (c.1856), French (v.) "perform oral sex on" (c.1917) and French kiss (1923) all probably stem from the Anglo-Saxon equation of Gallic culture and sexual sophistication, a sense first recorded 1749 in French novel. To take French leave, "depart without telling the host," is 1771, from a social custom then prevalent. However, in France this is said to be called filer à l'anglaise, lit. "to take English leave.""
Source and further information:
http://www.etymonline.com/index.php?search=%22Pardon+my+French%22&searchmode=none


2) ""Pardon my French" or "Excuse my French" is a common English language phrase ostensibly disguising profanity as French. The phrase is uttered in an attempt to excuse the user of profanity or curses in the presence of those offended by it under the pretense of the words being part of a foreign language.
The phrase has found large use in broadcast television and family films where less offensive words are preceded by "pardon my French" to emphasize their meaning without violating censorship or rating guidelines. A good example is in the movie Ferris Bueller's Day Off. Cameron calls Mr. Rooney and says, "Pardon my French, but you're an asshole." In another segment, Bueller says about Cameron, "Pardon my French, but if you were to shove a lump of coal up his ass, in two weeks you'd have a diamond.""

"Several expressions in French attempt to link various practices perceived as unsavory to England, e.g., "l'éducation anglaise" (disciplining children by sexually-tinged spanking). Ironically, several expressions are used by both the English and the French to describe the same unacceptable habit, but attributing the habit to the other people : e.g., "taking French leave" (leaving a party or other gathering without taking polite leave of one's host) is referred to in French as "filer à l'anglaise" (literally, "flee English-style"), while the (now somewhat archaic) expression "French letter" (referring to a condom) is rendered in French as "capote anglaise". During the 16th century in England, genital herpes was called the "French disease" and "French-sick" was a term for syphilis. These are also considered examples of Francophobia."
Source and further information:
http://en.wikipedia.org/wiki/Pardon_my_French


3) "It in fact originates from the constant warfare between England and France many years ago, at that time "French" was associated with indecent things and activies (Swearing, kissing etc)."
Source and further information:
http://www.urbandictionary.com/define.php?term=pardon+my+french


4) "French stereotyping is the root of "pardon my French," an excuse for foul language. The phrase emerged in the 1800s, according to the Oxford English Dictionary, but the practice of using French as an adjective to connote lewdness dates back to the 1500s. For centuries the French and English had a contentious relationship (as evidenced by all the wars). So the English, who considered the French oversexed, used the word to imply anything risque. For example, a French letter was a condom, and a French kiss, well, needs no explanation."
Source and further information:
http://www.newsweek.com/related.aspx?subject=St.+Louis&tid=relatedcl

I would guess it originated in Europe. There's always been a bit of a mutual loathing between the French and the English and coincidently, there's quite a few French sayings that do just this same thing by attaching unsavory things or words to the English.

Obviously, the English associated something "dirty" like swearing (basically mocking the French language) and associating it with filth or a bastardization of the supposed superior English language and culture.
Herpes were once called the "French disease" and "French-sick" was a term for syphilis.

But the French have sayings like "l'éducation anglaise" (disciplining children by sexually-tinged spanking).

Another similar phrase the English and French use interchangeably are "French Leave" or "filer à l'anglaise",(English Leave) and implies leaving a party without saying goodbye.

ever word in french is a bad word 0_0

I only say "pardon my French" after having yelled "MERDE!" or somesuch. If I say "scheisse" I ask to have my German pardoned, if I say "kuso" you'll have to pardon my Japanese. I don't really care who gets offended by my cussing in English, so I don't ask for pardon. ^_^

Probably because French are rather expressive when they talk.

I don't know for sure but I am guilty of it. I think it is to lighten up what might otherwise be something vulgar...when I swear for example (which is out of character and tends to shock people) I immediately say "pardon my French" and they relax and laugh. Maybe because we can pretend what I said isn't really what they think but a different language altogether and therefore the meaning is unknown. :)

Because, we as English speaking Americans need to blame someone for our faults. Who better to blame than the French? I mean, most swear words are no more French than French Fries, French Silk Pie, or French Pastries.