“God Rest Ye Merry, Gentlemen” has no known author or melody smith. It’s listed as a traditional 18th century carol and appears in many hymnals with many variations in lyric. The recording above uses five verses that seem mostly familiar and a little unfamiliar. I don’t think I’ve ever sung the fourth verse offered here or this verse I see in Hymns for a Pilgrim People:

“Fear not, then,” said the angel,
“Let nothing you affright;
This day is born a Savior
Of a pure virgin bright,
To free all those who trust in Him
From Satan’s pow’r and might.”