mid-15c., melwe, of fruit, "soft, sweet, juicy" (especially from ripeness), perhaps a variant of merow "soft, tender," from Old English mearu "soft, tender." General sense of "of ripe age or quality, perfected by maturing," from 1590s. Of color by 1560s; of sound, "soft, rich, or delicate to the perception," by 1660s. Meaning "slightly drunk, rendered good-humored or genial by intoxication" is from 1680s. Modern slang sense of "feeling good after smoking marijuana" is by 1946. Mellow yellow "banana peel smoked in an effort to get high" is from 1967. Related: Mellowly; mellowness.
1570s, "to ripen, bring to maturity" (transitive), from mellow (adj.). Intransitive sense of "become soft, be ripened" is from 1590s. Transferred sense of "give richness, flavor, or delicacy to" is from 1590s. Related: Mellowed; mellowing.
"strawy dung, loose earth, leaves, etc., spread on the ground to protect shoots or newly planted shrubs," 1650s, probably a noun use of Middle English molsh (adj.) "soft, moist" (mid-15c.), from Old English melsc, milisc "mellow, sweet," from Proto-Germanic *mil-sk- (source also of Dutch mals "soft, ripe," Old High German molawen "to become soft," German mollig "soft"), from PIE root *mel- (1) "soft."
early 15c., "relieve (pain); make mild or more tolerable; reduce in amount or degree," from Latin mitigatus, past participle of mitigare "soften, make tender, ripen, mellow, tame," figuratively, "make mild or gentle, pacify, soothe," ultimately from mitis "gentle, soft" + root of agere "to do, perform" (from PIE root *ag- "to drive, draw out or forth, move"). For mitis de Vaan suggests cognates in Sanskrit mayas- "refreshment, enjoyment," Lithuanian mielas "nice, sweet, dear," Welsh mwydion "soft parts," Old Irish min "soft," from a PIE *mehiti- "soft." Related: Mitigated; mitigating; mitigates.
1795, genus of small evergreen trees native to west Africa, introduced and nativized in New World tropics, from a Latinized form of a West African name of the tree (compare Temne kola, Mandingo kolo). The cola-nut contains much caffeine.
Meaning "carbonated soft drink" is 1919, short for Coca-Cola, Pepsi-Cola, and their many imitators. A 1900 publication ("Alcohol," by the Woman's Christian Temperance Union) lists the names of drinks found to contain caffeine and extract of coca leaf:
Afri Cola, Ala Cola, Cafe Coca, Carre Cola, Celery Cola, Chan Ola, Chera Cola, Coca Beta, Coca Cola, Pilsbury's Coke, Cola Coke, Cream Cola, Dope, Four Kola, Hayo Kola, Heck's Cola, Kaye Ola, Koca Nola, Koke, Kola Ade, Kola Kola, Kola Phos, Koloko, Kos Kola, Lime Cola, Lima Ola, Mellow Nip, Nerv Ola, Revive Ola, Rocola, Rye Ola, Standard Cola, Toka Tona, Tokola, Vim-O, French Wine of Coca, Wise Ola.