"O Come All Ye Faithful": A Jacobite Anthem?

This is a fascinating theory, tho' I doubt its veracity. I've included what Wikipedia has to say about the conjecture.

Claims of Jacobite connections[edit source]

Although, as previously stated, the hymn’s exact sources and origins remain unproven, there is universal agreement among musicologists that it was through the efforts of Catholic layman and music copyist John Francis Wade that it first appeared in print. Wade himself fled to France after the Jacobite rising of 1745 was crushed, and his liturgical books were often decorated with Jacobite imagery^[14] (for context, the aim of the rebellion had been to restore a Catholic monarch — Charles Edward Stuart, popularly known as “Bonnie Prince Charlie^[15]” — to the throne of England). These aspects of Wade’s life and political leanings have given rise to speculation that he might have intended for Adeste Fideles to be a ciphered birth ode to the Jacobite’s Young Pretender.

This theory regarding the hymn’s meaning has been most recently proposed by Professor Bennett Zon, head of music at Durham University. It essentially holds that “the song’s original Latin version was actually a coded rallying cry for the Steward cause”.^[16] Elements of this theory include:

• The as-yet-unproven but popular claim that “Bethlehem” was a common Jacobite cipher^[17] for England.
• The claim (also currently unproven) that Wade deliberately meant for the title Regem Angelorum — which is found in the hymn’s original Latin lyrics and translates literally to “King of Angels” — to refer to the king of England via a pun on the Latin words “Angelorum” (“of the angels”) and “Anglorum” (“of the English”).
• The fact that during the mid-18th century some English Roman Catholic liturgical books would place Adeste Fideles physically close to prayers for the would-be king in exile.^[18]

Proponents of this theory interpret the notions and circumstances described above as evidence that the lyrics of Adeste Fideles are meant to be “a call to arms for faithful Jacobites to return with triumphant joy to England (Bethlehem) and venerate the king of angels, that is, the English king (Bonnie Prince Charlie).”^[19] However, certain historical circumstances would seem to disprove or at least problematize the Jacobite ode theory. Namely:

1. The absence of any textual evidence that can conclusively prove that Wade explicitly composed Adeste Fideles as a piece of political propaganda. In the absence of such evidence, the Jacobite imagery found in Wade’s books might be merely an expression of the author’s idiosyncratic blend of political and religious thought, which in turn might have reflected the sentiments of Catholic Jacobites as a group.^[20]
2. Sources that credit the hymn’s composition to Wade overlook the fact that the exact origins of Adeste Fideles are uncertain. It is not known whether Wade might have simply copied the hymn from other sources (for instance, it could have been composed by Cistercian monks and eventually sung at the Portuguese embassy chapel in London^[21]), or to what extent he might have innovated on the contributions of the hymn’s other plausible authors.
3. Most of the hymn’s original lyrics are an almost-verbatim expression of Roman Catholic dogmas regarding the person of Jesus Christ. As stated elsewhere in this article, the hymn takes almost all its contents from Bible verses and the Nicene Creed.^[22] Indeed, the evidence that the hymn is merely an artistic expression of the Catholic spiritual and intellectual tradition is so readily evident that the Irish musicologist William H. Grattan Flood concluded that the words and music of the song “are to be attributed to a Catholic source and for Catholic worship”.^[23]