gloom n.

Old English glomung "twilight, the fall of evening," found but once (glossing Latin crepusculum), and formed (probably on model of æfning "evening") from glom "twilight," which is related to glowan "to glow" (hence "glow of sunrise or sunset"), from Proto-Germanic *glo- (see glow (v.)). Fell from currency except in Yorkshire dialect, but preserved in Scotland and reintroduced by Burns and other Scottish writers after 1785.

1580s, probably from gloom (n.) even though that word is not attested as early as this one. Shakespeare used it of woods, Marlowe of persons. Gloomy Gus has been used in a general sense of "sullen person" since 1902, the name of a pessimistic and defeatist newspaper comics character introduced about that time by U.S. illustrator Frederick Burr Opper. Related: Gloomily; gloominess.

1540s, "sullen, moody, frowning," from Middle English gloumen (v.) "become dark" (c. 1300), later gloumben "look gloomy or sullen" (late 14c.); see gloom. Or from or influenced by Low German glum "gloomy, troubled, turbid." In English the word was also formerly a noun meaning "a sullen look" (1520s). An 18c. extended or colloquial form glump led to the expression the glumps "a fit of sulkiness." Glunch (1719) was a Scottish variant. Related: Glumly; glumness.