> The Oxford English Dictionary defines conspiracy theory as "the theory that an event or phenomenon occurs as a result of a conspiracy between interested parties; spec. a belief that some covert but influential agency (typically political in motivation and oppressive in intent) is responsible for an unexplained event". It cites a 1909 article in The American Historical Review as the earliest usage example,[37][38] although it also appeared in print as early as April 1870.[39]

And it seems they even used time travel to do it.