Ungersven och havsfrun (as it is known in Swedish) or Herr Bøsmer i elvehjem (as it is known in Danish) (The Types of the Scandinavian Medieval Ballad A 49, Drink causes forgetfulness and makes man stay with mermaid) is a supernatural ballad type.[1] Known witnesses are edited in Sveriges Medeltida Ballader (no. 21) in ten Swedish variants (of which one is in Finland Swedish), from the mid-1700s onwards; five of the Swedish variants are recorded with melodies. It appears in Danmarks gamle folkeviser (no. 45), among the earliest manuscripts to contain it being Karen Brahes Folio.