From Old Norse ragnarǫkr 'twilight of the gods'.

• twilight from Late Middle English:

  A medieval combination of twi-, a form of two, and light. What significance ‘two’ has here is not entirely clear, though perhaps there is the idea of half-light, between day and night. In Scandinavian and German mythology the twilight of the gods is the destruction of the gods and the world in a final conflict with the powers of evil. English also uses the German and Old Norse equivalents Götterdämmerung and Ragnarök, the first of which is the title of the last opera in Richard Wagner's Ring cycle. Today, a twilight zone is primarily an urban area in a state of dilapidation or economic decline, but the term will forever be associated with the US television series The Twilight Zone, first shown in 1959. Each episode of the series offered a self-contained story with a science fiction or horror theme.