In modern usage, enthusiasm refers to intense enjoyment, interest, or approval expressed by a person.
The term is related to playfulness, inventiveness, optimism, zest, verve, and high energy.
[1] The word was originally used to refer to a person possessed by God, or someone who exhibited intense piety.
[4] During the years that immediately followed the Glorious Revolution, "enthusiasm" was a British pejorative term for advocacy of any political or religious cause in public, i.e. fanaticism.
"[5] During the 18th century, popular Methodists such as John Wesley or George Whitefield were accused of blind enthusiasm, a charge against which they defended themselves by distinguishing fanaticism from "religion of the heart."