Defining Conspiracy Theory

To truely understand how conspiracy theories originated, one must first understand the term and its original context.
The term was originally a neutral descriptor for any claim of civil, criminal or political conspiracy. (so mostly a political term used toward those who sought to swindle their way to the top) The first recorded use of the phrase "conspiracy theory" dates from 1909.
To conspire means "to join in a secret agreement to do an unlawful or wrongful act or to use such means to accomplish a lawful end." However, conspiracy theory is also used to indicate a narrative genre that includes a broad selection of (not necessarily related) arguments for the existence of grand conspiracies.
The word "theory" is, in this usage, sometimes considered to be more informal as in "speculation" or "hypothesis" rather than mainstream scientific theory. In fact scientists and academics veiw conspiracy theory with skeptism and have performed studies that go against these "theories" Also, the term conspiracy is typically used to indicate powerful figures, often of the Establishment, who are believed to be deceiving the population at large, as in political corruption.