The medieval poems describing Norse Ragnarok were composed in Old Norse.
Old Norse was the North Germanic language spoken in Scandinavia and Norse settlements during the Viking Age and the medieval period. The Icelandic manuscripts that preserve Völuspá and other Eddic poems were written in a western variety of Old Norse, often called Old Icelandic.
The surviving poems were written down centuries after some of their traditional material was likely first performed orally. This means the manuscripts preserve both ancient mythic themes and the language and literary conventions of medieval Iceland. The poems use distinctive alliteration, compressed imagery, and specialized poetic vocabulary.
Old Norse is not the same as modern Norwegian, Danish, Swedish, or Icelandic, although Icelandic retains especially strong connections to it. Latin appears in some medieval Scandinavian scholarly works, but it is not the original language of the Eddic poems themselves. Translations therefore depend on interpreting an older Germanic language and its poetic style.