Simplify the following text for a Grade 11 native English-speaking person.
Original: The term Edda ( Old Norse Edda , plural Eddur ) applies to the Old Norse Poetic Edda and Prose Edda , both of which were written down in Iceland during the 13th century in Icelandic , although they contain material from earlier traditional sources , reaching into the Viking Age .
Simplified: Edda or the plural Eddas or Eddur , including Poetic Edda ( or Older Edda ) and Prose Edda ( or Younger Edda ) , are two collections of stories about Viking deities . They were made in around 9th to 13th century by Icelandic Christian historians .