c. 1600, from French enthousiasme (16c.) and directly from Late Latin enthusiasmus, from Greek enthousiasmos "divine inspiration, enthusiasm (produced by certain kinds of music, etc.)," 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" (from PIE root *dhes-, forming words for religious concepts). It acquired a derogatory sense of "excessive religious emotion through the conceit of special revelation from God" (1650s) under the Puritans; generalized meaning "fervor, zeal" (the main modern sense) is first recorded 1716.
updated on October 13, 2021