John Anthony Scott and I have had many spirited exchanges on this song. Tony thinks the song originated with the shepherds of England and had no false dialect at all. But the poem by Ms Greene tells me a different tale.

I also have photocopy of a page from an 1890 hymnal that includes the song "De Massa Ob De Sheepfol'" with credit to Miss McLean --- with a tune credit to J.M. Whyte
The book is titled:

THE FINEST OF THE WHEAT
HYMNS OF THE NEW AND OLD
FOR MISSIONARY AND REVIVAL MEETING
AND SABBATH SCHOOLS

for C.C.McCabe, R.Sweeney, Wm. J.K. Kirkpatrick, the Whyte bros. of Canada and F.A. Hardin
63rd edition
edited by Geo. D. Elderkin
Chicago: R.R. McCabe & Co. publishers
@ 1890 by R.R. McCabe & George D. Elderkin

(Art Thieme)