- esoteric (adj.)
- 1650s, from Greek esoterikos "belonging to an inner circle," from esotero "more within," comparative adverb of eso "within," related to eis "into," en "in" (see en- (2)).
In English, originally of Pythagorean doctrines. According to Lucian, the division of teachings into exoteric and esoteric originated with Aristotle.