Jargon

The word jargon comes to English in the mid-14th century meaning unintelligible talk, gibberish, chattering, jabbering from Old French jargon (a chattering of birds). In the late 14th century, the verb jargounen (to chatter, to twitter) comes to Middle English from French.
 
Earlier, in the 12th century, Old French jargon also meant idle talk or ‘thieves’ Latin’. The word jargon is of echoic origin; that is, the word echoes a sound, for example, the sound of chattering birds. Latin has the word garrire or gaggire meaning to chatter.
 
In the 1640s, jargon was synonymous with ‘pidgin’ and ‘pidgin English’; that is, people from two different languages trying to communicate using sounds and body language.
 
Jargon meaning words and phrases used by a particular sect or profession is from the 1650s.
 
Reference: Online Etymological Dictionary, https://www.etymonline.com/
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