Enthusiasm
mid 16th century (in enthusiasm (sense 2)): via late Latin enthusiasmus ‘inspiration, frenzy’ from Greek enthousiasmos, from enthousiazein ‘be inspired or possessed by a god’ (based on theos ‘god’).
wiktionary
First attested from 1603, from Middle French enthousiasme, from Late Latin enthusiasmus, from Ancient Greek ἐνθουσιασμός(enthousiasmós), from ἐν(en, “in”) + θεός(theós, “god”) + οὐσία(ousía, “essence”).
etymonline
enthusiasm (n.)
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.
