TIn Scandinavian folklore, the Huldra (in Norwegian culture, derived from a root meaning "covered" or "secret"), or the skogsrå or skogsfru/skovfrue (meaning "Lady (read, counterpart of a Lord) of the forest") or Tallemaja (pine tree Mary) in Swedish culture, is a seductive forest creature. Her name suggests that she is originally the same being as the völva Huld and the German Holda. A male hulder is called a huldu, or in Norway a huldrekallhe huldra is one of several rå (keeper, warden), including the aquatic Sjörå (or havsfru), later identified with a mermaid, and the bergsrå in caves and mines who made life tough for the poor miners.
Associated with Christianity, a tale recounts how Eve had washed only half of her children when God came to her cottage; ashamed of the dirty ones, she hid them. God decreed that those she had hidden from him would be hidden from mankind; they became the huldrer.
...so the folklore goes.