Today, merry, as in “Merry Christmas,” suggests gaiety, a mood for celebration, but its original meaning was quite different.
For example, the carol we sing as “God Rest Ye, Merry Gentlemen,” should read “God Rest Ye Merry, Gentlemen.”
The word was at least four hundred years old when it was first written down in 1827, and at that time merry didn’t mean joyous, but rather, peaceful or pleasant.
So the original meaning of “Merry Christmas” is “Peaceful Christmas”.
The word “Merry” comes from the Middle English word “merie”.