Yours, Etc.: Origins and Uses of 8 Sign-Offs
literally "day of wrath," first words of Latin hymn of Last Judgment, attributed to Thomas of Celano (c.1250). See diurnal + ire.
(Latin: "Day of Wrath"), the opening words of a Latin hymn on the Last Judgment, ascribed to Thomas of Celano (d. c. 1256) and once forming part of the office for the dead and requiem mass.