enthusiasm [M16th] The origin of enthusiasm is Greek enthous ‘possessed by a god, inspired’, from theos ‘god’, which is the root of many words including atheist [M16th], pantheon [OE], and *theology. Until relatively recently enthusiasm, enthusiast, and enthusiastic had stronger and less favourable meanings than they do today. Enthusiasm was originally, in the early 17th century, religious mania or divine inspiration, often involving ‘speaking in tongues’ and wild, uncontrollable behaviour. An enthusiast was a religious fanatic or fundamentalist, or a hypocrite pretending to be one. Over the next hundred years or so the force of enthusiasm and its related words weakened so that they arrived at something like our modern meanings by the early 18th century, although the old senses persisted.