James J. Fuld writes in Th Book of World-Famous Music, 4th ed. (Dover, 1966, pp. 305-306):

"A possible source of this melody is Irene, Good Night, with music and words by Gussie L. Davis, sung by Edwin harley of Haverly's Mastodon Minstrels and published by Geo. Propheter, Jr., 20 W. 14th St., New York, N.Y., and 640 Race St., Cincinnati, Ohio, with copyright claims by the publisher of 1886 and 1887; JF. The melody line and words of the first two bars are the same as those set forth above [that is, a familar version], and the song is in 3/4 time, but the harmony is different throughout and the melody line and words do not resemble those of the well-known melody after the first two bars. As the 'feel' of the song is similar to the well-known melody, this song may either have been an adaptation of an existing folk song or have been the source for its later adaptation into a folk song. The melody is also known as Goodnight, Irene."

~Masato