aglow (adj.)youdaoicibaDictYouDict[aglow 词源字典]
1817 (in Coleridge), from a- (1) + glow. Figurative sense of "flushed with pleasurable excitement" is from 1830.[aglow etymology, aglow origin, 英语词源]
flush (v.1)youdaoicibaDictYouDict
mid-13c., flusshen "move rapidly or violently; rush, dart, spring" (intransitive); late 15c., flush up, transitive, "cause to fly; start or flush (birds)," perhaps imitative of the sound of beating wings.

The sense of "spurt, rush out suddenly, flow with force" (1540s, usually of water) probably is the same word, with the connecting notion being "sudden movement," but its senses seem more to fit the older ones of flash (v.), now all transferred to this word except in flash flood, via its variant flushe. OED considers this probably not connected to Old French flux. Transitive sense "cause to flow" is from 1590s.

Meaning "cleanse (a drain, etc.) with a rush of water" is from 1789. Of the face, "become suffused with warm color," from 1680s (flushed). Sense of "inflame with pride or passion" as a result of success, victory, etc., is from 1630s; perhaps influenced in sense by flesh (v). Related: Flushed; flushing.
red (adj.1)youdaoicibaDictYouDict
Old English read "red," from Proto-Germanic *raudaz (cognates: Old Norse rauðr, Danish rød, Old Saxon rod, Old Frisian rad, Middle Dutch root, Dutch rood, German rot, Gothic rauþs). As a noun from mid-13c.

The Germanic words are from PIE root *reudh- "red, ruddy" (cognates: Latin ruber, also dialectal rufus "light red," mostly of hair; Greek erythros; Sanskrit rudhira-; Avestan raoidita-; Old Church Slavonic rudru, Polish rumiany, Russian rumjanyj "flushed, red," of complexions, etc.; Lithuanian raudas; Old Irish ruad, Welsh rhudd, Breton ruz "red"). The only color for which a definite common PIE root word has been found. The initial -e- in the Greek word is because Greek tends to avoid beginning words with -r-.

Along with dead, bread (n.), lead (n.1), the vowel shortened in Middle English. The surname Read/Reid retains the original Old English long vowel pronunciation and is the corresponding surname to Brown-, Black, White.

The color designation of Native Americans in English from 1580s. The color as characteristic of "British possessions" on a map is attested from 1885. Red-white-and-blue in reference to American patriotism, from the colors of the flag, is from 1840; in a British context, in reference to the Union flag, 1852. The red flag was used as a symbol of defiance in battle on land or sea from c. 1600. To see red "get angry" is an American English expression first recorded 1898. Red rover, the children's game, attested from 1891. Red light as a sign to stop is from 1849, long before traffic signals. As the sign of a brothel, it is attested from 1899. As a children's game (in reference to the traffic light meaning) it is recorded from 1953.

Red-letter day (late 14c.) was originally a saint's day, marked on church calendars in red letters. Red ball signifying "express" in railroad jargon is 1904, originally (1899) a system of moving and tracking freight cars. Red dog, type of U.S. football pass rush, is recorded from 1959. Red meat is from 1808. Red shift in spectography is first recorded 1923. Red carpet "sumptuous welcome" is from 1934, but the custom for dignitaries is described as far back as Aeschylus ("Agamemnon"); it also was the name of a type of English moth.