It's not the "English language", the term "conspiracy theorist" was literally invented by the CIA to smear people who alleged the CIA was conspiring against the public.
The term "conspiracy theory" is itself the subject of a conspiracy theory, which posits that the term was popularized by the CIA in order to discredit conspiratorial believers, particularly critics of the Warren Commission, by making them a target of ridicule.
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The idea that the CIA was responsible for popularising the term "conspiracy theory" was analyzed by Michael Butter, a Professor of American Literary and Cultural History at the University of Tübingen.
