What is "finfolk"

n. sorcerous shapeshifters of the sea in Orkney folklore.

In Orkney folklore, Finfolk (sometimes Finnfolk) are sorcerous shapeshifters of the sea, the dark mysterious race from Finfolkaheem who regularly make an amphibious journey from the depths of the Finfolk ocean home to the Orkney Islands. They wade, swim or sometimes row upon the Orkney shores in the spring and summer months, searching for human captives. The Finfolk (both Finman and Finwife) kidnap unsuspecting fishermen, or frolicking youth, near the shore and force them into lifelong servitude as a spouse.