Slang, Idiom, Jargon, Euphemism or Argot?

In a recent post I was looking for the word that means a phrase used to avoid impolite words (euphemism) and ran across words like slang, idiom, and jargon.

That is a long list of words for words that are outside of formal expression. What is the difference?

Let's start with euphemism. A euphemism is the substitution of a more acceptable expression (usually a phrase) for one that might be viewed as offensive or harsh. George Carlin used the proliferation of euphemisms for several comedy routines. Dictionary.com uses the example "to pass away" for "to die." The substitutions dates from ancient Greece (from whence came the word), when words were avoided out of superstition. You probably remember Eumenides' substitution of "the Gracious Ones" for "the Furies."

When the word euphemism came into use in English in the 1650s it was rhetorical, indicating the use of a favorable term in place of an inauspicious one. It came from the Greek word eupemizein that means "speak with fair words, use words of good omen," according to etymonline.com. It was not until 1793 that the word began to be used for the replacement for an impolite word or phrase.

Slang, idiom jargon, and argot are different from euphemisms in that they are not intended to avoid embarrassment.

Slang words are those that are more playful or vivid and less acceptable in polite language. It also has a definition of "the jargon of a particular class, profession, etc." I would use jargon for the language peculiar to a specific profession. Slang came into use in English in 1756 to define the "special vocabulary of tramps or thieves." It may have come from the Norwegian word slengenamn, which meant nickname, but the Oxford English Dictionary says that based on "date and early associations" such etymology is unlikely.

Jargon is defined as "the language...peculiar to a particular trade, profession, or group." It is also used that is unintelligible, not understandable, or pedantic. Jargon is an old word, coming to English in the mid-1300s from an Old French world of the same spelling. The Old French used it for the chattering of birds, lending the sense of unintelligibility to the English word.

Argot is at the other end of the socioeconomic spectrum. While it can be (and is) used as a synonym for jargon, as language particular to a group and sometimes a profession or trade (more often of the genre of detectives noir), its strongest use is for language used particularly by gangsters and the underworld. Words like moll, gat, and gam are argot. Argot, like jargon, comes from French without change in spelling (or substantially in pronounciation). In French it referred to the language peculiar to the Parisian underworld. It arrived in English in 1860.

Idiom is language that (like euphemisms) has a meaning different from its components; dictionary.com uses the illustration of "kick the bucket" for the aforementioned euphemism "pass away." But it is also used (and in my experience more commonly) for language that is characteristic of the sentence construction of another language. Yiddish very often uses idiomatic expressions. My ancestry, Amish, is renowned for idiomatic expressions like "throw papa down the stairs his hat" or "throw the cow over the fence some hay." Idiom is also used of styles in music and literature. Idiom also comes to English from French, from the Middle French word idiome, which came from the Late Latin word idioma, that means "peculiar language." Latin got idoma from Greek, where it was also  idioma.