1871, nonsense word (perhaps based on jabber) coined by Lewis Carroll, for the poem of the same name, which he published in "Through the Looking-Glass." The poem is about a fabulous beast called the Jabberwock.
early 13c., chateren "to twitter, make quick, shrill sounds" (of birds), "to gossip, talk idly or thoughtlessly" (of persons), earlier cheateren, chiteren, of echoic origin. Compare Dutch koeteren "jabber," Danish kvidre "twitter, chirp." Of teeth, "make a rattling noise from cold or fright," mid-15c. Related: Chattered; chattering.
Phrase chattering class was in use by 1893, with perhaps an isolated instance from 1843:
Such was the most interesting side of the fatal event to that idle chattering class of London life to whom the collision of heaven and earth were important only as affording matter for "news!" [Catherine Grace F. Gore ("Mrs. Gore"), "The Banker's Wife," 1843]
"confusedly, hurriedly," 1590s, a "vocal gesture" [OED] probably formed from pig and the animal's suggestions of mess and disorder. Reduplications in the h-/p- pattern are common (as in hanky-panky, hocus-pocus, hinch(y)-pinch(y), an obsolete children's game, attested from c. 1600).
Edward Moor, "Suffolk Words and Phrases" (London, 1823), quotes a list of "conceited rhyming words or reduplications" from the 1768 edition of John Ray's "Collection of English Words Not Generally Used," all said to "signify any confusion or mixture;" the list has higgledy-piggledy, hurly-burly, hodge-podge, mingle-mangle, arsy-versy, kim-kam, hub-bub, crawly-mauly, and hab-nab. "To which he might have added," Moor writes, crincum-crankum, crinkle-crankle, flim-flam, fiddle-faddle, gibble-gabble, harum-scarum, helter-skelter, hiccup-suickup, hocus-pocus, hotch-potch, hugger-mugger, humdrum, hum-strum, hurry-scurry, jibber-jabber, prittle-prattle, shilly-shally, tittle-tattle, and topsy-turvy. Many of these date to the 16th century.