“Nothing great was ever achieved without enthusiasm,” Ralph Waldo Emerson
Enthusiasm first appeared in English in 1603 with the meaning “possession by God.” The source of the word is the Greek enthousiasmos, which ultimately comes from the adjective entheos, “having God within,” formed from en, “in, within,” and theos, “god.” Over time the meaning of enthusiasm became extended to “rapturous inspiration” (like that caused by a god), and eventually to the familiar sense “craze, excitement, strong liking for something.”
