History of the Term "Conspiracy Theory" The term "conspiracy theory" is used to describe any theory that attempts to characterize observed events as the result of some secret conspiracy. The term is often used dismissively, implying that the theory is implausible. Although conspiracy theories (particularly aimed at Jews and Bankers) date back hundreds of years, the earliest usage of "conspiracy theory" do not always have this connotation, although the theories are quite often dismissed in other ways. Usually it's simply a way of identifying the theory from other theories - as in "the theory that happens to have a conspiracy" The first usage I could find was from 1870, The Journal of mental science: Volume 16 - Page 141 1890 - Some kind of political conspiracy, mostly ridiculed http://books.google.com/books?id=ziIgAQAAMAAJ&dq="conspiracy theory"&pg=PA608-IA7#v=onepage&q="conspiracy theory"&f=false Here from a review of theories about the causes of the secession of the South, 1895. http://books.google.com/books?id=f9ghAQAAMAAJ&dq="conspiracy theory"&pg=PA394#v=onepage&q="conspiracy theory"&f=false Also on the same topic 1895 http://books.google.com/books?id=GkIxAQAAMAAJ&dq="conspiracy theory"&pg=RA16-PA27#v=onepage&q="conspiracy theory"&f=false Given the multiple usages on the subject of succession, it seems plausible that this is a key point in the evolution of the phrase. It shifts from simple incidental use in language to referring to a specific thing. From "that theory which has a conspiracy" to "the theory that we call conspiracy theory" 1899, this is more like it, from an article discussing various conspiracy theories regarding South Africa. And an early debunking: http://books.google.com/books?id=cHdNAAAAYAAJ&dq="conspiracy theory"&pg=PA227#v=onepage&q="conspiracy theory"&f=false Here it's seeming to move towards its current use with an implied "far-fetched" prepended. Some people get a bit upset when you use the term "conspiracy theory", so I think it's good to be clear on what you mean. One might say "I know it when I see it", like say 9/11 no-plane theories, or fake moon-landing theories. I think Aaronovitch has something right here: Aaronovitch, David (2010-01-19). Voodoo Histories: The Role of the Conspiracy Theory in Shaping Modern History (pp. 5-6). Penguin Group. Kindle Edition. Regarding the theory that the term was invented by the CIA in 1967, it might be useful to gather examples of usage from the decades before, and the decades after. Also an inflection point might be the JFK assassination itself on NOv 22, 1963. One 1962 reference is: Walter Wilcox. "The Press of the Radical Right: An Exploratory AnalysisJournalism & Mass Communication Quarterly - Walter Wilcox, 1962." Journals.sagepub.com, http://journals.sagepub.com/doi/pdf/10.1177/107769906203900202. Accessed 26 Aug. 2017. The referenced 1960 work by Baum seems to only exist in a few libraries. http://www.worldcat.org/title/consp...ical-right-in-the-united-states/oclc/18821548 It is however referenced by many books on conspiracy theories. Looking at this list of dissertation theses: http://crws.berkeley.edu/sites/default/files/shared/docs/ACADEMIC Theses & Dissertations Biblio 10-10-13.pdf there's lots of entries like: Common phrases are "The Conspiracy theory of History" and "The Conspiracy Theory of Politics". Both of these terms seem to most commonly refer to a world-wide Jewish conspiracy (theory) They mostly come after 1963 and 1967, but there's: This usage of "The conspiracy theory of..." may well date back to Karl Popper in "The Open Society and Its Enemies", 1950. In which he writes: It's worth noting the highly influential 1964 essay "The Paranoid Style in American Politics" which, while it does not use the term "conspiracy theory" still uses the word "conspiracy" in the context of this "paranoid style". http://archive.harpers.org/1964/11/pdf/HarpersMagazine-1964-11-0014706.pdf?