The _tune_ we now commonly use for "Hark the Herald Angels Sing" was composed by Felix Mendelssohn in the 1840s (for the Gutenberg Cantata that this blog post talks about) -- but the _lyrics_ were originally written in the 1730s by noted English Methodist Charles Wesley (who wrote many, many Christian hymns). The Wikipedia article on this song has a more accurate synopsis of its history:
Thanks for posting the actual history. This article is a ramble. The introduction is a mess of concepts and irrelevant links, the background is rushed and weakly researched, and the lyrics they fabricated are so removed from the original that it makes the headline clickbait. Kind of confused why it was even posted.
One thing about church music is that many melodies can be interchangeable. There is often a Metrical Index in your hymnal, and tunes are identified often by names (ALL CAPS) and metrical numbers. So it is often the case (Ode to Joy) that there are three sets of lyrics set to the same tune, as well as several different tunes to sing a single text (Mass parts take this to an extreme: how many ways to sing the Kyrie or Pater Noster?)
https://en.wikipedia.org/wiki/Hark!_The_Herald_Angels_Sing