"Shrove Tuesday, last day of carnival, day of eating and merrymaking before the fasting season of Lent," 1690s, French, literally "fat Tuesday," from mardi "Tuesday" (12c. in Old French, from Latin Martis diem "day of the planet Mars;" see Tuesday) + gras "fat," from Latin crassus, "thick," which is of unknown origin.
1530s, typical name for an English woman of the lower class, hence "girl, lass, sweetheart," sometimes also "strumpet," from the pet form of Isabel. Often paired with Tom, as Jill was with Jack. Colloquial St. Tibb's Eve (1785) was the evening of the last day, the Day of Judgment, hence "never."
1909 in the figurative sense of "complete overthrow" of something; from German Götterdämmerung (18c.), literally "twilight of the gods," from genitive plural of Gott "god" (see god) + Dämmerung "dusk, twilight," from PIE root *teme- "dark" (see temerity). Used by Wagner as the title of the last opera in the Ring cycle. It translates Old Norse ragna rok "the doom or destruction of the gods, the last day, world's end." A better transliteration is Goetterdaemmerung.
the last canonical service of the day, early 13c., cumplie, compelin, from Old French complie (12c.), from Medieval Latin completa, from Latin completa (hora), from completus (see complete (adj.)); with unetymological -n-. So called because the service usually completes the religious exercises of the day. Originally it was said after the evening meal and before retiring to bed, but in later medieval times it shifted to immediately after vespers.
"dining room," usually with reference to the room in which the Last Supper was held, c. 1400, from Old French cenacle, learned variant of cenaille (14c., Modern French cénacle), from Latin cenaculum "dining room," from cena "mid-day meal, afternoon meal," literally "portion of food," from PIE *kert-sna-, from root *sker- (1) "to cut." Latin cenaculum was used in the Vulgate for the "upper room" where the Last Supper was eaten. Related: Cenatical; cenation.
"in the time of, in the course of, throughout the continuance of," late 14c., duryng (earlier durand, mid-14c.), present participle of the long-obsolete verb duren "to last, endure, continue, be or exist" (mid-13c.), which is from Old French durer, from Latin durare "to harden," from durus "hard" (from PIE root *deru- "be firm, solid, steadfast"). During the day is "while the day endures," and the prepositional usage is a transference into English of a Latin ablative absolute (compare durante bello "during (literally 'enduring') the war").
In medieval England doomsday was expected when the world's age had reached 6,000 years from the creation, which was thought to have been in 5200 B.C.E. Bede, c. 720, complained of being pestered by rustici asking him how many years till the sixth millennium ended. However there is no evidence for the story of a general panic in Christian Europe in the year 1000 C.E.
Doomsday machine as the name of a hypothetical nuclear bomb powerful enough to wipe out human life (or all life) on earth is from 1960.