"mock-sun, an intensification of light on the solar halo," 1640s, from Greek parhelion "a mock-sun," from assimilated form of para- "beside" (see para- (1)) + hēlios "sun" (from PIE root *sawel- "the sun").
before vowels, par-, word-forming element, originally in Greek-derived words, meaning "alongside, beyond; altered; contrary; irregular, abnormal," from Greek para- from para (prep.) "beside, near; issuing from; against, contrary to," from PIE *prea, from root *per- (1) "forward," hence "toward, near; against." Cognate with Old English for- "off, away." Mostly used in scientific and technical words; not usually regarded as a naturalized formative element in English.
*sāwel-, Proto-Indo-European root meaning "the sun." According to Watkins, the *-el- in it originally was a suffix, and there was an alternative form *s(u)wen-, with suffix *-en-, hence the two forms represented by Latin sol, English sun.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit suryah, Avestan hvar "sun, light, heavens;" Greek hēlios; Latin sol "the sun, sunlight;" Lithuanian saulė, Old Church Slavonic slunice; Gothic sauil, Old English sol "sun;" Old English swegl "sky, heavens, the sun;" Welsh haul, Old Cornish heuul, Breton heol "sun;" Old Irish suil "eye;" Avestan xueng "sun;" Old Irish fur-sunnud "lighting up;" Old English sunne German Sonne, Gothic sunno "the sun."
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Harper, D. (n.d.). Etymology of parhelion. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/parhelion