The great Methodist hymnwriter Charles Wesley (1707-1788) published “Hymn for Christmas-Day” in 1743, in a compilation of Hymns and Sacred Poems for various occasions: prayers for the sick, congratulations on coming to faith, and many more. He intended his original, in ten stanzas, to be sung slowly to the tune Llanfair (“Christ the Lord is Risen Today,” without the Alleluias):

3. CHRIST, by highest Heaven adored
CHRIST, the Everlasting Lord,
Late in Time behold him come,
Offspring of a Virgin’s Womb.

4. Veiled in Flesh, the Godhead see,
Hail the Incarnate Deity!
Pleased as Man with Men to appear
JESUS our Immanuel here!

5. Hail the Heavenly Prince of Peace!
Hail the Sun of Righteousness!
Light and Life to All he brings,
Risen with Healing in his Wings.

6. Mild he lays his Glory by;
Born; that Man no more may die,
Born; to raise the Sons of Earth,
Born; to give them Second Birth.

7. Come, Desire of Nations, come,
Fix in Us thy humble Home,
Rise, the Woman’s Conquering Seed,
Bruise in Us the Serpent’s Head.

8. Now display thy saving Power,
Ruined Nature now restore,
Now in Mystic Union join
Thine to Ours, and Ours to Thine.

9. Adam’s Likeness, LORD, efface,
Stamp thy Image in its Place,
Second Adam from above,
Reinstate us in thy Love.

10. Let us Thee, though lost, regain
Thee, the Life, the Heavenly Man:
O! to All Thyself impart,
Formed in each Believing Heart.

 As we would expect from Wesley, the hymn is designed to give the singer lots of opportunity for detailed theological affirmation. There is no “Holly Jolly Christmas” in view; instead, we declare that Christ, the everlasting Lord, comes to us as the Godhead veiled in human flesh, and that he has laid aside his glory so that we may have a second birth and thus be raised above the power of death.

The hymn went through several minor adjustments, notably by evangelist George Whitefield (1714-1770), who over Wesley’s protests changed the first couplet to the words we know today.

As an interesting aside, there is a notable difference in the style of capitalization from what we use today. The nouns of all sorts are routinely capitalized; the names “God,” “Lord,” “Jesus,” and “Christ” are set in all caps; and yet pronouns referring to Jesus — “he,” “his,” “thy,” “thee,” and so on — are not capitalized. Almost not, anyway: in stanza 8 the word “Thine” is capitalized twice, and in stanza 10 the words “Thee” and “Thyself” are capitalized. And: “Us” is capitalized twice in stanza 7, and “Ours” twice in stanza 8. In other poems and hymns in the book this same variability of pronoun capitalization can be found: often with the human pronoun capitalized adjacent to a divine pronoun not capitalized.  If you are interested, here’s a link to a facsimile of Wesley’s Hymns and Sacred Poems; “Hymn for Christmas Day” is on pages 142-143.

In 1847, When William H. Cummings (1831-1915) was just in his mid-teens, he was a member of the chorus when Felix Mendelssohn (1809-1847) conducted the first London performance of the Elijah.

 Cummings went on to become a notable musician in his own right, and in 1855 he adapted a tune from Mendelssohn’s Festgesang as the setting universally known today.

Here’s Take 6’s a cappella version. https://www.youtube.com/watch?v=kWMmIzk4onw