Herr Tønne af Alsø ('Sir Tønne of Alsø') is a Danish ballad (The Types of the Scandinavian Medieval Ballad A 62; Danmarks gamle Folkeviser 34). Danmarks gamle Folkeviser records two versions: A (73 stanzas) and B (38); it also appears in Norway and Sweden. Dokumentasjonsprosjektet in Norway notes eight different variants, one dating back to the 1840s.
Summary
In the summary of The Types of the Scandinavian Medieval Ballad,
In the Swedish texts, the king is in Iceland rather than Uppsala, and in some of these Tønne rescues the sister, not the niece, of the mountain gnome's daughter.
References
Herr Tønne af Alsø Wikipedia(Text) CC BY-SA