"expounder of sacred mysteries," 1670s, from Late Latin hierophantes, from Greek hierophantes "one who teaches the rites of sacrifice and worship," literally "one who shows sacred things," from hieros "sacred," from PIE root *eis-, forming words denoting passion (see ire) + phainein "to reveal, bring to light" (from PIE root *bha- (1) "to shine"). In modern use, "expounder of esoteric doctrines," from 1822.
*bhā-, Proto-Indo-European root meaning "to shine."
It forms all or part of: aphotic; bandolier; banner; banneret; beacon; beckon; buoy; diaphanous; emphasis; epiphany; fantasia; fantasy; hierophant; pant (v.); -phane; phanero-; phantasm; phantasmagoria; phantom; phase; phene; phenetic; pheno-; phenology; phenomenon; phenyl; photic; photo-; photocopy; photogenic; photograph; photon; photosynthesis; phosphorus; phaeton; sycophant; theophany; tiffany; tryptophan.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit bhati "shines, glitters;" Greek phainein "bring to light, make appear," phantazein "make visible, display;" Old Irish ban "white, light, ray of light."