Here's the entry in the 1940 Hymnal Companion:

The text and tune of this Epiphany carol were both composed by John Henry Hopkins, Jr., in 1857, and first published in his Carols, Hymns, and Songs, 1863. It is given here without alteration of either text or harmonies. The composer has achieved the folk-song idion so completely that he has often been mistaken as the arranger only. The carol was adopted in the Hymnal of 1916, when a section devoted to carols was first introduced.