Well “hiisi” translates to “devil” but that’s very much a political translation as far as such things existed back then.
Translating “Hiisi” as “the Devil” is quite a fuck-the-pagans translation.
Hiisi (Finnish pronunciation: [ˈhiːsi]; plural hiidet [ˈhiːdet]) is a term in Finnic mythologies, originally denoting sacred localities and later on various types of mythological entities
Hiisi was originally a spirit of hill forests (Abercromby 1898). In Estonian hiis (or his) means a sacred grove in trees, usually on elevated ground. In the spells (“magic songs”) of the Finns the term Hiisi is often used in association with a hill or mountain, as a personage he also associated with the hills and mountains, such as the owner or ruler of the same. His name is also commonly associated with forests, and some forest animals.