mid-15c., of color, "shining brilliantly, splendid, very bright," from Old French resplendant and directly from Latin resplendentem (nominative resplendens) "brilliant, radiant," present participle of resplendere "to glitter, shine brightly," from re-, here perhaps an intensive prefix, + splendere "to shine, be splendid" (see splendid). In 16c.-17c. often resplendant. Related: Resplendently.
"vivid brightness, brilliance, splendor," early 15c., from Late Latin resplendentia, abstract noun from present-participle stem of Latin resplendens "brilliant, radiant" (see resplendent). Related: Respendency.
1590s, "shine more brightly than" (trans.), from out- + shine (v.). In this sense perhaps coined by Spenser. It was used in Middle English in an intransitive sense of "resplendent, shining forth" (late 14c.). Figurative sense of "to surpass in splendor or excellence" is from 1610s. Related: Outshone; outshining.
"arc of prismatic colors formed by the refraction of light rays by drops of rain or vapor," Middle English rein-bowe, from Old English renboga; see rain (n.) + bow (n.). Common Germanic compound (Old Frisian reinboga, Old Norse regnbogi, Swedish regenbåge, Dutch regenboog, German Regenbogen). The American rainbow trout (1876) is so called for its resplendent colors. Old English also had scurboga "shower-bow."
Old English scinan "shed light, be radiant, be resplendent, illuminate," of persons, "be conspicuous" (class I strong verb; past tense scan, past participle scinen), from Proto-Germanic *skeinanan (source also of Old Saxon and Old High German skinan, Old Norse and Old Frisian skina, Dutch schijnen, German scheinen, Gothic skeinan "to shine, appear"), which perhaps is from a PIE root *skai- "to shine, to gleam" (source also of Old Church Slavonic sinati "to flash up, shine"). Transitive meaning "to black (boots)" is from 1610s. Related: Shined (in the shoe polish sense), otherwise shone; shining.
c. 1500, "resplendent" (obsolete), from Latin flagrantem (nominative flagrans) "burning, blazing, glowing," figuratively "glowing with passion, eager, vehement," present participle of flagrare "to burn, blaze, glow," from Proto-Italic *flagro- "burning" (source also of Oscan flagio-, an epithet of Iuppiter), corresponding to PIE *bhleg-ro-, from *bhleg- "to shine, flash, burn" (source also of Greek phlegein "to burn, scorch," Latin fulgere "to shine"), from root *bhel- (1) "to shine, flash, burn." Sense of "glaringly offensive, scandalous" (rarely used of persons) first recorded 1706, probably from common legalese phrase flagrante delicto "while the crime is being committed, red-handed," literally "with the crime still blazing." Related: Flagrantly.