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c.1600, from Middle French enthousiasme (16c.) and directly from Late Latin enthusiasmus, from Greek enthousiasmos "divine inspiration," from enthousiazein "be inspired or possessed by a god, be rapt, be in ecstasy," from entheos "divinely inspired, possessed by a god," from en "in" (see en- (2)) + theos "god" (see Thea). Acquired a derogatory sense of "excessive religious emotion" (1650s) under the Puritans; generalized sense of "fervor, zeal" (the main modern sense) is first recorded 1716.