I'll quote Jackson's comment from another book:

 This [the version quoted] is a comparatively recent recording (around the beginning of the present century) of an extremely widely sung folk-tune. It appeares in Good Old Songs as a bare melody, no harmonic parts. I suggest, as an explanation of the d-flat in the fifth measure from the end, the intrusion of dorian influence. The earliest known recording among the fasola folk was in the first edition of the Sacred Harp, 1844. The negro adoptions and adaptations are reviewed WS [White Spirituals in the Southern Uplands] 251ff.
 The tune is quite evidently borrowed from secular environment. I list here a number of secular songs whose tunes are variously related: 'Barbar Allen', Sharp, i., 194 and 195; 'In Old Virginny', Sharp, ii., 232-234; 'Come All Ye Fair and Tender Ladies', Sharp, ii., 128-136; 'Katie Morey', Sharp, ii., 120; 'Dear Companion', Sharp, ii., 109; 'George Reilly', Sharp, ii., 26; 'Awake, Awake', Sharp, i., 358-364, and Petrie, Nos. 1222 and 265.
 A note on this song in the Social Harp says that the compiler, John G. McCurry, Hartwell, Georgia, "when eight years old, learned the air of this tune from Mrs. Catherine Penn." That was therefore in the year 1829.
 Text passages in the secular ballads which remind of those in the fasola song are seen in 'In Old Virginny', where we read:

 I am a man of constant sorrow,
 I have seen troubles all my days.
 I'll bid farewell to old Virginia,
 The place where I was partly raised.

 We see also in 'Awake, Awake', how the poor wayfaring stranger appears as "your true love" who "is going away."

(George Pullen Jackson, Spiritual Folk-Songs of Early America, 1937; Dover, 1964, pp. 71-72)

~Masato