

Except it is just scatting. The leekspin version and the Miku version of the song is just the scatting parts of the Loituma arrangement. The full Loituma version, Korpiklaani version or one of the many recorded versions from Finnish folk singers have the actual lyrics. They do actually include a scatted part, usually after every verse, but Loituma atleast extended it for a full verse of scatting, which the Miku version made into a full song.
For the record, the lyrics are about the main character of the song dancing polka with the girl he loves (Ieva), whose “proper” and religious parents don’t approve of the mc or dancing in general. So after they dance and go home, the mom of Ieva catches them and makes Ieva cry, the mc threatens the mom to leave them alone and professes his love for Ieva. Then they go on to dance more polka. It’s great.
Serial Experiments lain is my favourite anime, so I’d definetly recommend watching more… but if it’s just not for you it’s not going to click. For me, I enjoyed the anime already from the first few minutes and watched the whole thing on the edge of my seat in a single night.
Even when I didn’t understand anything on my first watch, I still enjoyed the visuals, audio, unique direction and storytelling, and really liked trying to make sense of it all and thinking about everything I just saw between episodes. Plus I could relate a lot to lain. But it’s definetly not for everyone.