1570s, "a fact directly observed, a thing that appears or is perceived, an occurrence," especially a regular kind of fact observed on certain kinds of occasions, from Late Latin phænomenon, from Greek phainomenon "that which appears or is seen," noun use of neuter present participle of phainesthai "to appear," passive of phainein "bring to light, cause to appear, show" (from PIE root *bha- (1) "to shine"). Meaning "extraordinary occurrence" is recorded by 1771. In philosophy, "an appearance or immediate object of experience" (1788). The plural is phenomena.
[Phenomenal] is a metaphysical term with a use of its own. To divert it from this proper use to a job for which it is not needed, by making it do duty for remarkable, extraordinary, or prodigious, is a sin against the English language. [Fowler]
1797, "the science of phenomena, as distinct from that of being;" 1840 as "a description or history of phenomena," the latter sense from German Phänomenologie, used as the title of the fourth part of the "Neues Organon" of German physicist Johann Heinrich Lambert (1728-1777), coined from Greek phainomenon (see phenomenon) + -logia (see -logy). Psychological sense, especially in Gestalt theory, is from 1930. Related: Phenomenological; phenomenologically.
*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."
23rd letter of the Greek alphabet. Its use for "psychic force, paranormal phenomenon" dates from 1942 (probably from psychic (adj.)).