Thanks for the reply, Ged Fox. I understood the lineage from "Stenka Razin" (1883, Dmitri Sadovnikov) to "River of My People" (1953, Pete Seeger) to The Carnival Is Over" (1965, Tom Springfield). It's possible that my source made the juxtaposition you suggested. Unfortunately, I can't find my notes on it.

All I can find now is the Wikipedia article on the person Stenka Razin, which says:
Stenka Razin is the hero of a popular Russian folk song, Ponizovaya Volnitsa, better known by the words Volga, Volga mat' rodnaya, Iz za ostrova na strezhen, and, simply, Stenka Razin. The words were written by Dmitri Sadovnikov (??????? ?????????? ??????????) in 1883; the music is folk.

I suppose that "the music is folk" could mean that Sadonikov wrote it as a poem and it was later made into a song but the composer's name has been forgotten. But it could also mean that Sadonikov wrote the words around an existing tune that he liked, just as Seeger and Springfield did.