I came across an interesting article by Gerry Hanson about Christmas Carols in the This England magazine. I often find these at Half Price Books and always snatch them up.
As a child in England, I spent many evenings leading up to Christmas, with friends, singing English Folk Carols door to door. We were often given treats and a few coins and followed the evening spending our pennies on a bag of chips at the local fish and chip shop.
Apparently, singing carols was a pagan tradition associated with the passing of the winter solstice. They were banned in the English churches until the late 1600s. In 1700 While Shepherds Watched wasn't allowed to be used in Church of England services until an approved list of permitted carols was introduced in 1782 including Hark the Herald Angels Sing. The Carol was often sung by children with different versions and in 1936 after the abdication of Edward VIII children sang: Hark! the herald Angels sing - Mrs. Simpson's pinched our king.
Isaac Watts (1674-1748) after complaining that hymns sung in church were dull, began at an early age to write more than 700 hymns including Joy to the World.
Phillip Brooks, after spending Christmas Eve in Bethlehem, was inspired to write O Little Town of Bethlehem.
Silent Night is by far the most popular of carols sung at Christmas time.