There's no definitive history behind Christmas caroling. Where they originated, who wrote them and how they evolved is unclear. Caroling is an oral tradition, passed down from generation to generation.
Carols commemorating the nativity, or birth of Jesus Christ, were purportedly first written in Latin in the 4th and 5th centuries, but they didn't become associated with Christmas until the 13th century. Saint Francis of Assisi, the Roman Catholic saint of animals and the environment, is often credited with incorporating upbeat Latin hymns into Christmas services. The energetic, joyful carols were sung in sharp contrast to the somber Christmas music of the day. The concept of Christmas carols, and spreading them to the community to celebrate Christ's birth, is thought to have spread across Europe.
Today, many caroling groups sing for charity in churches and neighborhoods; some historical accounts claim this is rooted in feudal societies, when poor citizens would "sing for their supper" in exchange for food or drink. Another theory is that carolers traveled door-to-door because they were not originally allowed to perform in churches. Others say this idea didn't develop until the 16th century, when Anglo-Saxon peasants adapted these pagan customs when they went wassailing, requesting nourishment from their superiors in exchange for singing good tidings.
Wassail was a thick, hot spiced beverage that helped keep the traveling well-wishers warm; in its heyday, the drink was just as much of a holiday tradition as eggnog is in modern times. As wassailing evolved, with children often going door-to-door, it became more associated with Christmas and caroling. Oliver Cromwell banned Christmas celebrations in England from 1649 to 1660 (he believed Christmas should be a serious holiday, and celebrated accordingly), and caroling did not experience a surge in popularity until the 19th century, when it's thought that the joyful, expressive hymns were well-received in the Victorian Era.
A common legend says that Christmas carols were named after Carol Poles, a little English girl who supposedly went missing in London during the holiday season in the late 19th century. People supposedly searched for her by going door-to-door, singing to declare their good intentions. Although it may be a nice story, it has no factual basis.