Jargon
late Middle English (originally in the sense ‘twittering, chattering’, later ‘gibberish’): from Old French jargoun, of unknown origin. The main sense dates from the mid 17th century.
wiktionary
From Middle English jargoun, jargon, from Old French jargon, a variant of gargon, gargun(“chatter; talk; language”).
jargon (plural jargons)
etymonline
jargon (n.)
mid-14c., "unintelligible talk, gibberish; chattering, jabbering," from Old French jargon "a chattering" (of birds), also "language, speech," especially "idle talk; thieves' Latin" (12c.). Ultimately of echoic origin (compare Latin garrire "to chatter").
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.
