They are a cover of a Finnish folk song named ievan polkka, which was originally sung by the Finnish band Loituma in four parts. At the Kostin Folk Music Festival from 65438 to 0997, Leutuma sang this song "Ievan Polkka" in the form of Acabella, and then this song began to attract everyone's attention. However, until 2006, this song was only known in a few European countries such as Finland.

Loituma is a folk band from Finland, with four members singing in four parts. Their songs are mainly traditional Finnish music. She has attracted much attention for attending 1997 Kostin Folk Music Festival. Anita Lehtola, the lead singer, is a female singer with a charming voice. She often participates in all kinds of world music. Anita's singing means Runo-song (also called Runo-Song) and Rune means ancient Nordic and Finnish poems. This is a kind of Finnish folk poetry, which is repetitive in form and rhymes at the beginning. It is cold and charming, as if it brought us to a green land, which is far away and just a fantasy.

I will give you a link. Http://www.ergeal.ru/archive/mp3/Loituma-Levas_polka.mp3, listens to the original song.