In the background of the menu screen in Skyrim, a song called the Song of the Dragonborn. The song has lyrics in another language, which I believe is in-universe. What is it?
It is sung in Dovahzul ("Dragon-Voice"), the Dragon Language or Dragonish.
Here is the song with translation if you're curious: http://www.ign.com/wikis/the-elder-scrolls-5-skyrim/Song_Of_The_Dragonborn
More reading on the Dragon language: http://elderscrolls.wikia.com/wiki/Dragon_Language