The Christmas carol service was invented in Truro in 1880 by a chap called Edward WhiteBenson. The story goes that on Christmas Eve everybody in Truro would get disgustingly drunk, and that the Bishop of Truro (Benson) was so disgusted that he decided to lure everybody out of the pub and into the church with his new service.

The problem with this story is that there’s no evidence that that’s what motivated Benson. And we do know a lot about him. He later became Archbishop of Canterbury and his whole family had something of a mania for writing. His wife had 39 lesbian lovers. How do we know that? Because she kept a diary, and numbered them. One of his sons was the eminent gay novelist EF Benson. Another was the eminent gay poet Arthur Benson. 

Arthur wrote the words to Land of Hope and Glory. He also wrote a diary of four million words, which is often reckoned to be the longest ever. His daughter Margaret was an eminent lesbian Egyptologist. His daughter Nellie actually stole one of her own mother’s girlfriends and died of TB.

Astoundingly, there were no grandchildren. 

Anyway, in 1880 this family, or rather this hive of oversexed logomania, was in the brand‐new diocese of Truro. It was so brand new that they didn’t even have a cathedral, just a large shed, and Edward White Benson decided to invent the carol service, perhaps not to get the people out of the pubs, but to get the carols out.
You see, before this, Christmas carols hadn’t been sung in the church, they’d been sung in the pub. Carols were folk songs; originally they were folk dances (that’s what ‘carol’ meant: ‘a dance in a ring’).

Why would you see three ships come sailing by? The answer is that nobody knows

This is why so many of them are really rather odd. Why would you see three ships come sailing by? The answer is that nobody knows. It was just a song that in some versions involved Jesus on Christmas day in the morning, and in other versions involved three pretty girls on New Year’s Day. It doesn’t make any sense anyway as a Christmas hymn because Bethlehem is landlocked. The same thing goes for The Holly and the Ivy. There is a religious version, but there are also versions that are just about holly and ivy, and the fascinating question of which one is better.

Hark! Who goes there?

Then in the 18th and 19th Centuries folklorists started to collect these folk songs and smarten them up, and people started to write new ones. But even these new ones were a bit incoherent and the versions changed all the time. For example, the co‐founder of Methodism Charles Wesley wrote a beautiful carol that began:

Hark how all the welkin rings
Glory to the King of Kings
Peace on earth and mercy mild
God and sinners reconciled.

And that’s how the carol went for 20 years, until another preacher called George Whitefield published a new version that went:

Hark, the herald angels sing Glory to the new-born King!

Wesley was not in the slightest bit amused by this (probably because the Bible is quite clear that the herald angels who appear to the shepherds saytheir news, they don’t sing it). He wrote that he didn’t want
to be held “accountable either for the nonsense or for the doggerel of other men”. But he is. Look in any hymnbook and Hark the Herald Angels Sing will be clearly listed: words by Wesley, tune by Mendelssohn.

We have been carolling away against the explicit wishes of both the lyricist and the composer

Mendelssohn would be even more perplexed and vexed by the whole thing. He died without ever even hearing of the hymn. All he did was to write a song about Gutenberg. It was precisely 400 years since the invention of the printing press and Mendelssohn knocked out a song about it. However, he realised that once the anniversary had passed, it would probably need some new words as songs about type aren’t that popular. He wrote in a letter
that he didn’t mind what new words were written just so long as they weren’t religious. Then he died, and a few years later somebody noticed that the tune would work very well with Hark the Herald Angels Sing and that was that. And ever since then people have been carolling away unaware that they are going against the explicit, written wishes of both the lyricist and the composer. 

Bohemian rhapsody

Good King Wenceslas is an even odder business. Good King Wenceslas was a real chap, except he wasn’t a king and he wasn’t called Wenceslas, but he may have been good. His name was Vaclav and he was Duke of Bohemia in the 10th Century. Poor little Vaclav had a difficult childhood. His father died when he was a child and he was brought up partly by his mother and partly by his paternal grandmother. These two ladies did not get along at all well, especially as his mother was pagan and his grandma was Christian. Eventually, his mother solved the problem by the time‐honoured method of dealing with difficult mothers-in-law: she had her assassinated – strangled with a veil, to be precise. Then Vaclav came of age and employed the time‐honoured method of dealing with overbearing mothers: he exiled her.

After that Vaclav started his career of do‐goodery. He would potter about his dukedom, especially at night, giving stuff to the poor. An early biography says:“Rising every night from his noble bed, with bare feet and only one chamberlain, he went around to God’s churches and gave alms generously to widows, orphans, those in prison and afflicted by every difficulty, so much so that he was considered, not a prince, but the father of all the wretched.” 

Given that he was the duke, I would have thought that he could just free the prisoners. And I don’t think much of prisons that anybody can break into in the middle of the night. Mind you, I also don’t see what he had against shoes; and I shall never know now that he’s dead. 

If I had a brother named Boleslaus the Cruel, I would watch out

You see, Vaclav still had one family member left, his brother Boleslaus the Cruel. Now, if I had a brother with a name like that, I would watch out. It’s a dead giveaway. I would employ bodyguards. I would watch my back like a hawk. But Vaclav didn’t and Boleslaus and a few of his friends assassinated him in 935. It is a sad truth, but a certain one, that Good King Wenceslas did not look out. 

But where (I hear you cry) was Wenceslas’ faithful page in all this, the one who followed him around in the snow? Well, his name was Podevin and he doesn’t seem to have been there at the assassination; instead he showed his Christian charity by taking out one of the assassins in a revenge killing before being chased, cornered in a forest, and killed.

Boleslaus was still wiping the blood off his lance when he was told that his wife had given birth to a son. So he called him Strachkvas, which means ‘Dreadful Feast’. Then he got on with being cruel and the Bohemians started to get all nostalgic for the days of Vaclav. Soon Vaclav was declared a saint, and then he was posthumously declared king by Otto the Great. 

There’s something so Christmassy about Jingle Bells even though it never mentions Christmas

Then, 500 years later, someone in Finland wrote a song about the coming of spring. It was a nice, bouncy tune with nice bouncy words, but it was Finnish and nobody noticed what a good melody it was until 300 years after that, when an Englishman called John Mason Neale found the obscure Finnish tune and the obscure (in England) Bohemian saint and put the two together. Why the hell he did this, nobody really knows, but he did and it was published in 1853. Neale was an odd chap. He once wrote a history of church pews.

There’s just something so timelessly English about Away in a Manger, O Little Town of Bethlehem and We Three Kings, even though they’re all from the US. There’s something so Christmassy about Wenceslas and Ding Dong Merrily on High and Jingle Bells even though none of them mentions Christmas, and Jingle Bells (which is also American) was written about Thanksgiving.

 But somehow these carols work, and so do all the others. It may be something to do with Edward White Benson’s skill in laying out the carol service, or it may be the eggnog.

Extracted from A Christmas Cornucopia by Mark Forsyth © 2016, published by Viking.

If you would like to comment on this story or anything else you have seen on BBC Culture, head over to our Facebook page or message us on Twitter.

And if you liked this story, sign up for the weekly features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Earth, Culture, Capital, Travel and Autos, delivered to your inbox every Friday.