> 1.a. 1756– The special vocabulary used by any set of persons of a low or disreputable character; language of a low and vulgar type. (Now merged in sense 1c.)
1.b. 1801– The special vocabulary or phraseology of a particular calling or profession; the cant or jargon of a certain class or period.
1.c. 1818– Language of a highly colloquial type, considered as below the level of standard educated speech, and consisting either of new words or of current words employed in some special sense.
1.d. 1805– Abuse, impertinence. (Cf. slang v. 3, 4.)