Jargon
Etymology
From Old French jargon, meaning "a chattering, the twittering of birds," of imitative origin — the word mimics unintelligible noise. Early English used it for gibberish or any speech one couldn’t follow. Only later did it settle on its modern sense: the in-group technical vocabulary that sounds, to the uninitiated, exactly like birdsong.
noun · /JAR-gun/
The specialized vocabulary of a profession or field, often opaque to outsiders.
What it names
The precise-but-exclusionary shorthand every trade develops — efficient for insiders, a wall for everyone else.
Example
Stripped of consulting jargon, "leverage our synergies" turned out to mean "work together."
Related idea
Jargon is the technical vocabulary of a profession; argot is the private, often deliberately secretive language of a closed social group. Surgeons have jargon; pickpockets have argot.