Origin: 1275–1325; Middle English dismale unlucky time, dismol day one of two days in each month considered unlucky (hence later taken as adj.) < Anglo-French dis mal < Medieval Latin diēs malī literally, evil days
c.1400, from Anglo-Fr. dismal, from O.Fr. (li) dis mals "(the) bad days," from M.L. dies mali "evil or unlucky days" (also called dies Ægyptiaci), from L. dies "days" (see diurnal) + mali, pl. 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. Modern sense of "gloomy, dreary" first recorded in English 1590s, in reference to sounds. Related: Dismally.