'Conspiracy' is Latin for 'breathing together' — plotters with heads bent close, whispering.
A secret plan by a group to do something unlawful or harmful; the action of plotting or conspiring.
From Old French 'conspiracie,' borrowed from Latin 'cōnspīrātiō' (agreement, unanimity, concord; a conspiracy, a plot), the noun of action from 'cōnspīrāre' (to breathe together, to blow together, to agree, to plot in concert), composed of 'con-' (together, in common) + 'spīrāre' (to breathe, to blow). 'Spīrāre' derives from PIE *speys- (to blow, to breathe), the same root that produced 'spirit' (breath, soul), 'inspire' (to breathe into), 'expire' (to breathe out), 'respire,' and 'aspire' (to breathe toward, to aim at). The noun preserves the full semantic arc of the Latin verb: from literal harmonious
The phrase 'conspiracy theory' was first used in the 1870s as a neutral legal and journalistic term for a theory that a conspiracy had occurred. It became pejorative in the mid-twentieth century, especially after the Warren Commission report on the Kennedy assassination (1964), when 'conspiracy theory' began to imply irrationality or paranoia. The term's shift from neutral description to dismissive label happened within living memory
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