What's the "een" in Halloween?
c.1600, "pertaining to possession by a deity," from Greek enthousiastikos "inspired," from enthousiazein (see enthusiasm). Meaning "pertaining to irrational delusion in religion" is from 1690s. The main modern sense, in reference to feelings or persons, "intensely eager, rapturous," is from late 18c. Related: Enthusiastically.