French Kiss

A French kiss is a kiss in which one participant's tongue touches the partner's lips or tongue and usually enters his or her mouth. A French kiss is a slow passionate kiss which is usually considered intimate, romantic, erotic or sexual. A French kiss is generally considered an erotic kiss usually reserved for lovers.
In many parts of the world, this kind of kissing as a public display of affection is discouraged and may even be regarded as taboo. A French kiss is often used in cinema to indicate sexual desire between lovers.
 

Etymology

It is believed that a French kiss is so-called because at the beginning of the 20th century the French had a reputation for more adventurous and passionate sex practices. In France, it is referred to as baiser amoureux ("love kiss") or baiser avec la langue ("kiss with the tongue"), even if in past times it was also known as baiser florentin ("Florentine kiss"). In French slang, a French kiss is called a patin (ice skating shoe) or a galoche (wooden-soled shoe). Doing a French kiss is referred to rouler un patin ("roll a skate", as in ice skating shoe) or rouler une pelle ("roll a shovel") or s'emballer in slang.
A French kiss is referred to in Private Lindner’s Letters,^[1] a collection of items gathered during World War I and published in 1939:

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 between tongues. (Not to be confused with French kissing.)

—Clarence R. Lindner

 

Erotic kiss

A "kiss with the tongue" stimulates the partner's lips, tongue and mouth, which are sensitive to the touch. The practice is often considered a source of pleasure. The oral zone is one of the principal erogenous zones of the body, and the tongue is more erogenous than the lips.

Researchers report that French kissing of many partners during adolescence can significantly increase the risk of meningitis.^[2] However, this is probably due to kissing increasing the risk of getting mononucleosis and mononucleosis having the chance to develop into meningitis.