when people say a curse word, why do they say ''pardon my french''. what does ''french'' have to do with it?

It sort of has to do with sarcasm. It simply indicates a different language is used- sarcastically, since it's not.

When saying "pardon my french" one is attempting to disguise the curse word as a part of another language.

This phrase, in which French refers to "bad language", is employed

when the speaker feels compelled to use an obscenity despite having

listeners who might be offended. It's a late 19th century euphemism

which first appeared in Harper's Magazine in 1895.

It is thought that the term French is employed in this sense as it

already had a history of association with things considered vulgar.

As far back as the early 16th century, French pox and the French

disease were synonyms for genital herpes, and French-sick was another

term for syphillis. The OED [Oxford English Dictionary] also equates

the adjective French with "spiciness", as in French letter for

"condom", French kiss (1923) and French (i. e. "sexually explicit")

novels (from 1749).

this is my guess:

In the 1950's, cursing was considered to be a major taboo, so the speaker would actually curse in French to be more polite. In these instances, "Pardon my French" would refer to actual French.

The reason is quite simple really...the french language has a reputation for containing one of the most colorful swear words evolved from Latin....the former primary language in Europe.

Got start meeting more french people dude. When ever they are saying anything loud it sounds like they are angry.

Check out Quebec.

There's an old tradition of assigning 'dirty' or impolite things to the French: french kiss, french disease (STD), etc.

i think in french le f..ck means the seal

We say it because Frenchies say "Pardon my English".

I'm not kidding thats true.

the french are dirty and their mouths are filthy