The phrase “rest you merry” has nothing to do with Christmas. It dates back to Medieval England–as early as 1300, when it was used in a romantic tale called “Floris and Blauncheflur.” Of course, that was in Old English, and much harder to read today.
By 1548, English Bishop Thomas Cooper referred to it in the Latin dictionary, “Bibliotheca Eliotae,” and made clear that it was term used by the common people for “be glad or joyful.”
In 1599, Shakespeare used the expression when William says goodbye to Touchstone in Act 5. The song we know today is from the Elizabethan era, and it was a common way of greeting someone or saying farewell.
By the time the reference showed up in the Christmas carol, it had come to mean “a state of pleasant happiness.” So, when folks in the 1600’s sang the song, they were hoping the gentlemen (and women) would be kept in a state of pleasant, harmonious, joy by God as a result of all the amazing things that happened on Christmas Day.
When the song was finally written down in 1760, the phrase had fallen out of use, and the publisher made the very egregious error of misplacing the comma. What should have been a song of encouragement to find joy and happiness to a group of gentlemen instead turned into a song about hoping a group of happy gentlemen find some rest.
But the wonderful fact is that the idea of “resting merry” was never intended to be something you did for just one month of the year. It was meant to be a way of life, a wish for people you cared for. Not just at Christmas, but every single day of your life.
Duane S. Montague 