Di sma undar jordi, or simply di sma, are legendary vættir

Vættir

Vættir or wights are nature spirits in the Norse religion. These nature spirits divide up into 'families', including the Álfar , Dvergar , Jötnar , and even gods, the Æsir and Vanir, who are understood to be prominent families among them. The term 'families' is often translated as 'clans' or...

-like creatures found in folklore

Scandinavian folklore

Scandinavian folklore is the folklore of Sweden, Norway, Denmark, Iceland, the Faroe Islands, and the Swedish speaking parts of Finland.Collecting folklore began when Gustavus Adolphus of Sweden sent out instructions to all of the priests in all of the parishes to collect the folklore of their area...

 from the island of Gotland

Gotland

Gotland is a county, province, municipality and diocese of Sweden; it is Sweden's largest island and the largest island in the Baltic Sea. At 3,140 square kilometers in area, the region makes up less than one percent of Sweden's total land area...

, Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

. The name can roughly be translated as "the small ones underground". Di sma are said to take care of farms and the people and animals that live there, as long as one does not anger them. The most classical example of doing so is to mindlessly scald them when disposing hot water outdoors. According to Gotlandic tales, di sma can only be seen by looking through a hole in a sheet of paper.

The Swedish band Di sma undar jårdi, active in the 1980s, was named after these creatures.