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mid-15c., melwe "soft, sweet, juicy" (of ripe fruit), perhaps related to melowe, variant of mele "ground grain" (see meal (2)), influenced by Middle English merow "soft, tender," from Old English mearu. Meaning "slightly drunk" is from 1680s. Mellow yellow "banana peel smoked in an effort to get high" is from 1967. Related: Mellowly; mellowness.
1570s, from mellow (adj.). Related: Mellowed; mellowing.
(also mellow) To become relaxed and easy: wondering why the family in ''The Grapes of Wrath'' didn't move to LA and mellow out/ Even the testiest groups and crews can be mellowed out after spending time at Alpine (1970s+ Students)