"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."
c. 1300, "messenger on foot," agent noun from run (v.). The meaning "one who runs, a racer" is from early 14c.
With many technical senses. The meaning "smuggler, one who risks or evades dangers, impediments, or legal restrictions" is by 1721; the sense of "police officer" is from 1771. The botanical meaning "rooting stem of a plant" is from 1660s. The sense of "embroidered cloth for a table" is from 1888. In baseball, "a base-runner," by 1845.
also frontrunner, of political candidates, 1908, American English, a metaphor from horse racing (where it is used by 1901 of a horse that runs best while in the lead).
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.
late Old English þræl "bondman, serf, slave," from a Scandinavian source akin to Old Norse þræll "slave, servant," figuratively "wretch, scoundrel," probably from Proto-Germanic *thrakhilaz, literally "runner," from root *threh- "to run" (source also of Old High German dregil "servant," properly "runner;" Old English þrægan, Gothic þragjan "to run"). Meaning "condition of servitude" is from early 14c.
"type of grallatorial bird with a long, slender, curved bill," mid-14c., curlu, from Old French courlieu (13c., Modern French courlis), said to be imitative of the bird's cry but apparently assimilated with corliu "runner, messenger," from corre "to run," (from Latin currere "to run, move quickly," from PIE root *kers- "to run"). The bird is a good runner. In Middle English the word sometimes also meant "quail," especially in Bible translations.