December 20th is observed as Go Caroling Day  

St. Francis of Assisi is credited for popularizing Christmas carols.  In 1223, he started his Nativity Plays in Italy. They were presented in the people's own language, not Latin. The new carols spread to France, Spain, Germany and other European countries.  St. Francis inspired the composers to write more Christmas music. 

They were usually sung in homes, pubs and streets, 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. 

Before carol singing in places like churches became popular, there were sometimes official carol singers called 'Waits'. They were called 'Waits' because they sang on Christmas Eve, in remembrance of shepherds were watching their sheep when the angels appeared to them. 

Lord, make me an instrument of Your peace. 
      ------St. Francis of Assisi

 . . . . speaking to one another in psalms and hymns and spiritual songs, singing and making melody in your heart to the Lord.
      ------Ephesians 5:19

Carrie Underwood singing Do you Hear What I Hear

https://www.bing.com/videos/search?q=do+you+hear+what+i+hear+youtube&view=detail&mid=B4F381F6130059A33C91B4F381F6130059A33C91&FORM=VIRE0&ru=%2fsearch%3fq%3ddo%2byou%2bhear%2bwhat%2bi%2bhear%2byoutube%26form%3dANNTH1%26refig%3dc8de42731b07471f86a12484229996e0%26sp%3d1%26qs%3dEP%26pq%3ddo%2byou%2bhear%2bwhat%2bi%2bhear%2byou%26sk%3dPRES1%26sc%3d8-27%26cvid%3dc8de42731b07471f86a12484229996e0

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Resource:

https://www.whychristmas.com/customs/carols_history.shtml