yellowyoudaoicibaDictYouDict[yellow 词源字典]
yellow: [OE] Yellow is a member of an ancient and widespread family of European colourterms descended from Indo-European *ghel-, *ghol-, which denoted both ‘yellow’ and ‘green’. From it were descended Latin helvus ‘yellowish’ and possibly galbus ‘greenishyellow’ (source of French jaune ‘yellow’ and English jaundice), Greek kholé ‘bile’ (source of English choleric, melancholy, etc), Russian zheltyj ‘yellow’, Lithuanian geltonas ‘yellow’, and English gall and gold.

In the Germanic languages it has produced German gelb, Dutch gel, Swedish and Danish gul, and English yellow. A yolk [OE] is etymologically a ‘yellow’ substance.
=> choleric, gall, gold, jaundice, melancholy, yolk[yellow etymology, yellow origin, 英语词源]
yellow (adj.)youdaoicibaDictYouDict
Old English geolu, geolwe, "yellow," from Proto-Germanic *gelwaz (cognates: Old Saxon, Old High German gelo, Middle Dutch ghele, Dutch geel, Middle High German gel, German gelb, Old Norse gulr, Swedish gul "yellow"), from PIE *ghel- (2) "to shine," with derivatives referring to bright materials and gold (see glass). For other Indo-European "yellow" words, see Chloe.

Occasionally in Middle English used of a color closer to blue-gray or gray, of frogs or hazel eyes, and to translate Latin caeruleus, glauco. Also as a noun in Old English. Meaning "light-skinned" (of blacks) first recorded 1808. Applied to Asiatics since 1787, though the first recorded reference is to Turkish words for inhabitants of India. Yellow peril translates German die gelbe gefahr. Sense of "cowardly" is 1856, of unknown origin; the color was traditionally associated rather with jealousy and envy (17c.). Yellow-bellied "cowardly" is from 1924, probably a semi-rhyming reduplication of yellow; earlier yellow-belly was a sailor's name for a half-caste (1867) and a Texas term for Mexican soldiers (1842, based on the color of their uniforms). Yellow dog "mongrel" is attested from c. 1770; slang sense of "contemptible person" first recorded 1881. Yellow fever attested from 1748, American English (jaundice is a symptom).
yellow (v.)youdaoicibaDictYouDict
Old English geoluwian "to become yellow," from the source of yellow (adj.). Transitive sense from 1590s. Related: Yellowed; yellowing.