c.1400, from Anglo-French dismal (mid-13c.), from Old French (li) dis mals "(the) bad days," from Medieval Latin dies mali "evil or unlucky days" (also called dies Ægyptiaci), from Latin dies "days" (see diurnal) + mali, plural of malus "bad" (see mal-).Through the Middle Ages, calendars marked two days of each month as unlucky, supposedly based on the ancient calculations of Egyptian astrologers (Jan. 1, 25; Feb. 4, 26; March 1, 28; April 10, 20; May 3, 25; June 10, 16; July 13, 22; Aug. 1, 30; Sept. 3, 21; Oct. 3, 22; Nov. 5, 28; Dec. 7, 22). Modern sense of "gloomy, dreary" first recorded in English 1590s, in reference to sounds. Related: Dismally.