Kumbaya: History of an Old Song February 6, 2018 by Stephen Winick, the American Folklife Center Archive at the Library of Congress
"although a Gullah Geechee origin is certainly still possible, we can't be fully confident that the song originated in Gullah, rather than in African American English more generally. But it is certainly likely that Gullah Geechee versions led to it becoming a popular song today.
"In summary, then, the evidence from the American Folklife Center Archive does not fully support any of the common claims about the origin of "Kumbaya." Instead, it suggests that "Kumbaya" is an African American spiritual which originated somewhere in the American south, and then traveled all over the world: to Africa, where missionaries sang it for new converts; to the northwestern United States, where Marvin Frey heard it and adapted it as "Come By Here"; to coastal Georgia and South Carolina, where it was adapted into the Gullah dialect. It was likely versions in Gullah Geechee dialect that made it to the Northeastern United States, where it entered the repertoires of such singers as Pete Seeger and Joan Baez; and eventually to Europe, South America, Australia, and other parts of the world, where revival recordings of the song abound. Although it is truly a global folksong, its earliest versions are preserved in only one place: the AFC Archive."