 The History of Christmas Carols
The History of Christmas Carols 
  Carols were first sung in Europe thousands of years ago, but these  were not Christmas Carols. They were pagan songs, sung at the Winter  Solstice celebrations as people danced round stone circles. The Winter  Solstice is the shortest day of the year, usually taking place around  the 22nd December. The word Carol actually means dance or a song of  praise and joy! Carols used to be written and sung during all four  seasons, but only the tradition of singing them at Christmas has really  survived!
  Early Christians took over the pagan solstice celebrations for  Christmas and gave people Christian songs to sing instead of pagan ones.  In AD 129, a Roman Bishop said that a song called 'Angel's Hymn' should  be sung at a Christmas service in Rome. Another famous early Christmas  Hymn was written, in 760AD, by Comas of Jerusalem for the Greek Orthodox  Church. Soon after this many composers all over Europe started to write  carols. However, not many people liked them as they were all written  and sung in Latin, a language that the normal people couldn't  understand. By the time of the Middles Ages (the 1200s), most people had  lost interest in celebrating Christmas altogether.
          
 
 
This was changed by St. Francis of Assisi when, in 1223, he started his 
Nativity Plays in 
Italy.  The people in the plays sang songs or 'canticles' that told the story  during the plays. Sometimes, the choruses of these new carols were in  Latin; but normally they were all in a language that the people watching  the play could understand and join in! The new carols spread to France,  Spain, Germany and other European countries. 
    The earliest carol, like this, was written in 1410. Sadly only a very  small fragment of it still exists. The carol was about Mary and Jesus  meeting different people in Bethlehem. Most Carols from this time and  the Elizabethan period are untrue stories, very loosely based on the  Christmas story, about the holy family and were seen as entertaining  rather than religious songs. They were usually sung in homes rather than  in churches! Traveling singers or Minstrels started singing these  carols and the words were changed for the local people wherever they  were traveling. One carols that changed like this is 
'I Saw Three Ships'.
  When Oliver Cromwell and the Puritans came to power in England in  1647, the celebration of Christmas and singing carols was stopped.  However, the carols survived as people still sang them in secret. Carols  remained mainly unsung until Victorian times, when two men called  William Sandys and Davis Gilbert collected lots of old Christmas music  from villages in England. 
          
 
 
Before carol singing in public became popular, there were sometimes  official carol singers called 'Waits'. These were bands of people led by  important local leaders (such as council leaders) who had the only  power in the towns and villages to take money from the public (If others  did this, they were sometimes charged as beggars!). They were called  'Waits' because they only sang on Christmas Eve (This was sometimes  known as 'watchnight' or 'waitnight' because of the shepherds were  watching their sheep when the angels appeared to them.), when the  Christmas celebrations began.
            Also, at this time, many orchestras and choirs were being set up in  the cities of England and people wanted Christmas songs to sing, so  carols once again became popular. Many new carols,such as 
'Good King Wenceslas', were also written .
  
 
  
New  carols services were created and became popular, as did the custom of  singing carols in the streets. Both of these customs are still popular  today! One of the most popular types of Carols services are Carols by  Candlelight services. At this service, the church is only lit by  candlelight and it feels very Christmassy! Carols by Candlelight  services are held in countries all over the world.
          Perhaps the most famous carol service, is the service of Nine Lessons  and Carols from King's College in Cambridge, UK. This service takes  place on Christmas Eve and is broadcast live on BBC Radio (and all over  the world). In my house, we listen to it and it means Christmas has  really started!! The Service was first performed in 1918 as a way of the  college celebrating the end of the First World War. It is always  started with a single choir boy singing a solo of the first verse of the  Carol 'Once in Royal David's City'. 
Sing along to Once in Royal David's City!  (on a different site) A service of Nine Lessons and Carols, has nine  bible readings (or lessons!) that tell the Christmas story with one or  two carols between each lesson. Sometimes you get carol services which  are a combination of nine lessons and carols and carols by candlelight!  So you have nine lessons and carols by candlelight!
Source: 
https://www.whychristmas.com/customs/..._history.shtml