I recently learned that Carol of the Bells (as it is known in English-speaking countries) was originally a Ukrainian song called Shchedryk.

From Wikipedia:

"Shchedryk" (Ukrainian: ??????, from ?????? ???i?, "Bountiful Evening") is a Ukrainian shchedrivka, or New Year's song, known in English as "The Little Swallow". It was arranged by composer and teacher Mykola Leontovych in 1916, and tells a story of a swallow flying into a household to sing of wealth that will come with the following spring. "Shchedryk" was originally sung on the night of January 13, New Year's Eve in the Julian Calendar (December 31 Old Style), which is Shchedry Vechir. Early performances of the piece were made by students at Kyiv University.

"Shchedryk" was later adapted as an English Christmas carol, "Carol of the Bells", by Peter J. Wilhousky following a performance of the original song by Alexander Koshetz's Ukrainian National Chorus at Carnegie Hall on October 5, 1922. Wilhousky copyrighted and published his new lyrics (which were not based on the Ukrainian lyrics) in 1936, and the song became popular in the United States and Canada, where it became strongly associated with Christmas.

The music is in the public domain; Wilhousky's lyrics, however, are under copyright owned by Carl Fischer Music.

There are lots of recordings out there:

https://www.youtube.com/results?search_query=Shchedryk

https://www.youtube.com/results?search_query=Carol+of+the+Bells

And a few Mudcat threads, for example: Origins: Carol of the Bells (Shchedrik)