What is "vaettir"

Vættir (Old Norse; singular Vættr) or wights are nature spirits in Norse mythology. These nature spirits are divided up into 'families', including the Álfar (elves), Dvergar (dwarves), Jötnar (giants), and even gods, the Æsir and Vanir, who are understood to be prominent families among them. The term 'families' ( ættir) is often translated as 'clans' or 'races'. These families sometimes intermarried with each other, and sometimes with humans. Sjövættir (sea spirits) or vatnavættir (water spirits) are guardians of the specific waters.'''

Húsvættir (house wights) is a collective term for keepers of the household, like the English brownie and the Swedish tomte. The tomte or nisse is a solitary vätte, living on the farmstead. He is usually benevolent and helpful, which can not be said about an innately mischievous illvätte. However, a nisse can cause a lot of damage if he is displeased or angry, including killing of livestock or causing serious accidents.