Ragnarok n.

Middle English reken "to emit smoke," of smoke or stench, "to rise," from Old English recan (Anglian), reocan (West Saxon) "emit smoke," from Proto-Germanic *reukan (source also of Old Frisian reka "smoke," Middle Dutch roken, Dutch rieken "to smoke," Old High German riohhan "to smoke, steam," German rauchen "to smoke," riechen "to smell"); from the same source as the nouns (see reek (n.)).

Originally a strong verb, with past tense reac, past participle gereocen, but occasionally showing weak conjugation in Old English. Meaning "to emit a bad smell" is recorded from 1710 via sense "be heated and perspiring" (early 15c.). Related: Reeked; reeking.

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.