glum

Etymology 1

Probably from Middle Low German glum (“glum”), related to German dialectal glumm (“gloomy, troubled, turbid”). More at gloomy.

adj

1. despondent; moody; sullen
   […] and the prospect of three more days of teaching before the weekend break, Mr. MacPherson felt unusually glum. 1959, Mordecai Richler, The Apprenticeship of Duddy Kravitz
   A glummer look replaced the already glum look on Arthur Dent's face. 1982, Douglas Adams, Life, the Universe and Everything, page 23

Etymology 2

From Middle English glomen, glommen, glomben, gloumben (“to frown, look sullen”), from *glom (“gloom”). More at gloom.

verb

1. (obsolete) To look sullen; to be of a sour countenance; to be glum.
   upon me he gan to loure and glum, Enforcing him so for to ryse withall, But that I shortly unto hem did cum, 1509, Stephen Hawes, The Passetyme of Pleasure

noun

1. (obsolete) sullenness
   That they be deaf and dumb, And play silence and glum c. 1550, John Skelton, Colyn Cloute