Do you know ghouls from goblins and ghosts?
1756, "special vocabulary of tramps or thieves," later "jargon of a particular profession" (1801), of uncertain origin, the usual guess being that it is from a Scandinavian source, cf. Norwegian slengenamn "nickname," slengja kjeften "to abuse with words," literally "to sling the jaw," related to Old Norse slyngva "to sling." But OED, while admitting "some approximation in sense," discounts this connection based on "date and early associations." Liberman also denies it, as well as any connection with French langue (or language or lingo). Rather, he derives it elaborately from an old slang word meaning "narrow piece of land," itself of obscure origin. Century Dictionary says "there is no evidence to establish a Gipsy origin." Sense of "very informal language characterized by vividness and novelty" first recorded 1818.
[S]lang is a conscious offence against some conventional standard of propriety. A mere vulgarism is not slang, except when it is purposely adopted, and acquires an artificial currency, among some class of persons to whom it is not native. The other distinctive feature of slang is that it is neither part of the ordinary language, nor an attempt to supply its deficiencies. The slang word is a deliberate substitute for a word of the vernacular, just as the characters of a cipher are substitutes for the letters of the alphabet, or as a nickname is a substitute for a personal name. [Henry Bradley, from "Slang," in "Encyclopedia Britannica," 11th ed.]A word that ought to have survived is slangwhanger (1807, American English) "noisy or abusive talker or writer."
Expressions that do not belong to standard written English. For example, “flipping out” is slang for “losing one's mind” or “losing one's temper.” Slang expressions are usually inappropriate in formal speech or writing. (See jargon.)
A style or register of language consisting of terms that can be substituted for standard terms of the same conceptual meaning but having stronger emotive impact than the standard terms, in order to express an attitude of self-assertion toward conventional order and moral authority and often an affinity with or membership in occupational, ethnic, or other social groups, and ranging in acceptability from sexual and scatological crudity to audacious wittiness (see Preface)
[mid-1700s+ British; origin unknown; probably related to sling, which has cognates in Norwegian that suggest the abusive nature of slang; the British dialect original term slang meant both ''a kind of projectile-hurling weapon'' and ''the language of thieves and vagabonds,'' reinforcing the connection with ''sling'']