In Norse mythology, (; ) is a series of events, including a great battle, foretelling the death of numerous great figures (including the gods Odin, Thor, Týr, Freyr, Heimdall, and Loki), natural disasters, and the submersion of the world in water. After these events, the world will rise again, cleansed and fertile, the surviving and returning gods will meet and the world will be repopulated by two human survivors. is an important event in Norse mythology and has been the subject of scholarly discourse and theory in the history of Germanic studies. The event is attested primarily in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda, written in the 13th century by Snorri Sturluson. In the Prose Edda and in a single poem in the Poetic Edda, the event is referred to as (), a usage popularised by 19th-century composer Richard Wagner with the title of the last of his Der Ring des Nibelungen operas, (1876), which is "Twilight of the Gods" in German. Etymology The Old Norse compound word has a long history of interpretation. Its first element, , is unproblematic, being the genitive plural of (n. pl.) "the ruling powers, gods." The second element is more problematic, as it occurs in two variants, and . Writing in the early 20th century, philologist Geir Zoëga treats the two forms as two separate compounds, glossing as "the doom or destruction of the gods" and as "the twilight of the gods." The plural noun has several meanings, including "development, origin, cause, relation, fate." The word as a whole is then usually interpreted as the "final destiny of the gods." The singular form is found in a stanza of the Poetic Edda poem Lokasenna, and in the Prose Edda. The noun means "twilight" (from the verb "to grow dark"), suggesting a translation "twilight of the gods." This reading was widely considered a result of folk etymology, or a learned reinterpretation of the original term due to the merger of (spelled ǫ) and (spelled ø) in Old Icelandic after c. 1200 (nevertheless giving rise to the calque "Twilight of the Gods" in the German reception of Norse mythology). Other terms used to refer to the events surrounding in the Poetic Edda include ( means age, "end of an age") from a stanza of , from two stanzas of , ("when the gods die") from ,