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.

https://en.m.wikipedia.org/wiki/Hiisi

I think “the Fae” would be a more accurate translation, theology-wise.