French Kissing is to kiss and to touch tongues. The term does not come from France and the term was cited in love letters and became a term on its own.
The term 'French Kiss' is cited in Private Lindner’s Letters: Censored and Uncensored of 1918:
So I have decided to become a linguist. Being able to read French fluently and speak it wretchedly, and to speak German connectively but not to read it at all, I am taking up Luxembourg, which is a wonderful blend of the two, a sort of liaison [sic] between tongues. (Not to be confused with French kissing.)
refers to a strongly modified style of servant’s dress that evolved from typical maids’ black and white afternoon uniforms of the nineteenth century (and their later use by stereotypical characters in risqué burlesque dramas of the bedroom farce variety). The designs of the French maid dress can range widely from a conservative look to very revealing. It is now often associated with cosplay, sexual roleplaying, and fetishism. Depending on design details, some forms can be classified as lingerie.