Middle English shour, from Old English scur, scura "a short fall of rain, storm, tempest; fall of missiles or blows; struggle, commotion; breeze," from Proto-Germanic *skuraz (source also of Old Norse skur, Old Saxon and Old Frisian scur "fit of illness;" Old High German scur, German Schauer "shower, downpour;" Gothic skura, in skura windis "windstorm"), from PIE root *kew-(e)ro- "north, north wind" (source also of Latin caurus "northwest wind;" Old Church Slavonic severu "north, north wind;" Lithuanian šiaurus "raging, stormy," šiaurys "north wind," šiaurė "north").
By Middle English in the general sense of "a copious supply bestowed": Of blood, tears, etc., from c. 1400. Of meteors from 1835. Sense of "bath in which water is poured from above" is recorded by 1851 (short for shower-bath, itself attested from 1803). The meaning "large number of gifts bestowed on a bride" (1904, American English colloquial) later was extended to the party at which it happens (1926). Shower-curtain is attested from 1914.
"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."
1570s, "come down in showers;" 1580s, "to discharge a shower on; wet copiously with or as with liquid sprayed," from shower (n.1). Intransitive sense of "take a shower" is by 1930. Related: Showered; showering.
"one who or that which shows or exhibits," Middle English sheuer "watchman, overseer" (senses now obsolete), later "revealer, interpreter, one who points out or exhibits" (c. 1300), from Old English sceawere "spectator, watcher; mirror," agent noun; see show (v.), also for the sense evolution.
1784, literally "rainbow-colored," coined from Latin iris (genitive iridis) "rainbow" (see iris). The verb iridesce (1868) is a back-formation. Related: Iridescently.
late 14c. as the name of a flowering plant (Iris germanica); early 15c. in reference to the eye membrane, from Latin iris (plural irides) "iris of the eye; iris plant; rainbow," from Greek iris (genitive iridos) "a rainbow;" also "iris plant" and "iris of the eye," a word of uncertain origin, traditionally derived from PIE root *wei- "to bend, turn, twist."
Iris was the name of the minister and messenger of the Olympian gods (especially of Hera), visibly represented by the rainbow (which was regarded as the descent of a celestial messenger). From the oldest parts of the Iliad the word is used of both the messenger and the rainbow.
The eye region was so called (early 15c. in English) for being the part that gives color to the eye; the Greek word was used of any brightly colored circle, "as that round the eyes of a peacock's tail" [Liddell & Scott]. Another sense in Middle English was "prismatic rock crystal." Related: Iridian; iridine.
[move quickly in search of something], c. 1300, scouren, a word of uncertain origin, probably from Old Norse skyra "rush in," related to skur "storm, shower, shower of missiles" (see shower (n.)). This was likely influenced by or blended with Old French escorre "to run out," from Latin excurrere (see excursion).
The sense also probably has been influenced by scour (v.1) "cleanse by hard rubbing" and entangled with it in some figurative uses and in phrases such as scour the countryside "clear (a place) of enemies or undesirable persons." Middle English also had it as a noun, as in the expression in good scour "quickly, with all haste" (c. 1300).
silver-white metallic element, 1804, coined in Modern Latin by its discoverer, English chemist Smithson Tennant (1761-1815) from Greek iris (genitive iridos) "rainbow" (see iris) + chemical ending -ium. So called "from the striking variety of colours which it gives while dissolving in marine acid" [Tennant]