From Middle English blew, blewe, from Anglo-Norman blew, from Middle French bleu, from Old French blöe, bleve, blef (“blue”), from Frankish *blāu (“blue”) (perhaps through a Late Latin blāvus, blāvius (“blue”) attested from Isidore of Seville), from Proto-Germanic *blēwaz (“blue, dark blue”), from Proto-Indo-European *bʰlēw- (“yellow, blond, grey”). Cognate with dialectal English blow (“blue”), Scots blue, blew (“blue”), North Frisian bla, blö (“blue”), Saterland Frisian blau (“blue”), Dutch blauw (“blue”), German blau (“blue”), Danish, Norwegian Bokmål, Norwegian Nynorsk, and Swedish blå (“blue”), Faroese bláur (“blue”), Icelandic blár (“blue”), Latin flāvus (“yellow”), French bleu (“blue”), Middle Irish blá (“yellow”). Doublet of blow. Possibly related also to English blee (“colour”), from Old English blēo (“colour”); but direct derivatives of Proto-Germanic *blēwaz (“blue, dark blue”) in Old English include: Old English blāw and blēo (“blue”), Old English blǣwen (“bluish, light-blue”), blǣhǣwen (“blue-coloured, bluish, violet or purple colour”, literally “blue-hued”). There seems to be a parallel connection in Germanic between words for blue and colour, dually exemplified by Proto-West Germanic *blīu (“colour, blee”) and *blāu (“blue”); and Proto-Germanic *hiwją (“colour, hue”) and *hāwī (“blue, purple”). (depressed): Compare typologically Russian тоска́ зелёная (toská zeljónaja) (<+ зелёный (zeljónyj)). Also compare фиоле́тово (fiolétovo).

miserable • unhappy • atrabiliary • atrabilious • blitheless • dispirited • blue • bummed out • chapfallen • cheerless • chopfallen • crestfallen • cut up • damp • dejected • depressed • despondent • disgruntled • disconsolate • disheartened • dismal • doleful • dolesome • down • down in the dumps • down in the mouth • downcast • downhearted • downsome • dull • elegiac • elegious • forlorn • gloomy • glum • grief-stricken • grieving • heavy-hearted • heartsore • heartsick • inconsolable • infelicitous • jawfallen • joyless • lachrymose • lamentful • low • low-spirited • lugubrious • lumpish • melancholic • melancholy • moody • mopey • morose • mournful • passionate • plaintive • Plutonian • Plutonic