"chatter inconsequentially, talk foolishly or idly," early 15c., praten, from or related to Middle Dutch praten "to chatter" (c. 1400), from a Proto-Germanic imitative root (compare East Frisian proten, Middle Low German praten, Middle High German braten, Swedish prata "to talk, chatter"). Transitive sense of "say or tell in a prating manner" is from late 15c. (Caxton). Related: Prated; prating. As a noun, idle, childish talk," from 1570s.
From 1640s as "mixed speech, pigin;" 1650s as "phraseology peculiar to a sect or profession," hence "mode of speech full of unfamiliar terms." Middle English also had it as a verb, jargounen "to chatter" (late 14c.), from French.
late 14c., litarge, "state of prolonged torpor or inactivity, inertness of body or mind," from Medieval Latin litargia, from Late Latin lethargia, from Greek lēthargia "forgetfulness," from lēthargos "forgetful," apparently etymologically "inactive through forgetfulness," from lēthē "a forgetting, forgetfulness" (see latent) + argos "idle" (see argon). The form with -th- is from 1590s in English. The Medieval Latin word also is the source of Old French litargie (Modern French léthargie), Spanish and Italian letargia.
1530s, "scullion, kitchen knave," of uncertain origin. Perhaps in reference to military units or attendants so called for the color of their dress or their character; more likely originally a mock-military reference to scullions and kitchen-knaves of noble households, of black-liveried personal guards, and of shoeblacks. See black (adj.) + guard (n.). By 1736, sense had emerged of "one of the idle criminal class; man of coarse and offensive manners." Hence the adjectival use (1784), "of low or worthless character."
c. 1300, cesen, "to stop moving, acting, or speaking; come to an end," from Old French cesser "to come to an end, stop, cease; give up, desist," from Latin cessare "to cease, go slow, give over, leave off, be idle," frequentative of cedere (past participle cessus) "go away, withdraw, yield" (from PIE root *ked- "to go, yield"). Transitive sense "put a stop to," now rare, is from late 14c. Related: Ceased; ceasing. Old English in this sense had geswican, blinnan.