The song is based on an old Finnish lullaby.
Thanks for posting that one! What's funny is that even though it's the "standard Finnish folk melody" (or what I will always think of as "Veljo Tormis's Laulusild melody", LOL), for some reason what it also reminds me of is the soundtrack to the Georgian-Estonian movie Mandariinid:
and while the music for that soundtrack was written by a Georgian composer and I don't know whether or not he had any intention of making it sound Estonian at all or purely Georgian (and anyway that's not Finnish), if he did I think he did it brilliantly, because it sounds Georgian but also sounds like it could (almost) work as a melody for either Estonian or Finnish folksongs too. (And if he didn't, well, then never mind. But they go nicely together.)