The word slang entered the language in 1756, meaning special vocabulary of tramps or thieves. By 1801 it had generalized to mean jargon of a given profession, & these days it mostly means casual, informal, or playful speech. Etymologists seem to agree that slang’s origin is unknown, though two probable sounding (& interesting) theories have been disproved. The first is that the word slang has a relationship to the word language, in particular the French word langue. As logical as that seems, linguistic forensics don’t’ support it. Another disproved theoretical origin is the Norse term slengja kljeften. Its literal translation is to sling with the jaw & its meaning is to abuse with words. It warms my heart to know that as I type, hardworking etymologists are chipping away in the word mines trying to get to the bottom of this mystery.
A near-synonym of slang is jargon. It came to English in the 1300s meaning unintelligible talk or gibberish. It came from Old French, in which jargon meant chattering, especially of birds, which came from the Latin word garrire, which also meant chatter.
In the 1650s the word lingo came to English. Lingo was probably a corruption of the Latin term lingua franca, a medium of communication between two peoples.
The word patois, which carries a somewhat positive connotation in modern English, started out just the opposite. It came to English meaning a provincial dialect, & carried all the cultural baggage associated with living far from the assumed center of culture. Its most likely source is the Old French word patoier, or to paw or handle clumsily.
A somewhat less judgmental term was the word vernacular, which simply meant native to a country, & showed up in the 1600s from the Latin word vernaculus, or native, local, indigenous.
Ah, nothing like a little slang, eh? Please leave any comments in the comments section.