Merry Christmas 实际上起源于英国一个名字叫John Calcott Horsely 的人。英国人当年在19世纪初的时候互送贺卡的时候，都是人工做的卡片，上面写上祝福的话的。 可是当年Horsely 则是第一个批量印刷Christmas card 的人， 而他本人就是写的Merry Christmas 的， 以后人们都如法炮制，沿用至今。
1、merry 以有趣和快乐为特征的或令人感到有趣和快乐的；欢乐的。
如：a merry joke 逗乐的笑话?
2、happy 指愉快的，快乐的：享受、显示或表现出快乐、满足或欢乐的。
happy有时表示“快乐”的升级：幸福。
happy life：幸福生活。
两种说法没区别，谈不上哪个是固定短语 ，但Merry Christmas 比较地道。
扩展资料：
圣诞节的来历：
Christmas is of course a religious festival. It’s all about celebrating the birth of Jesus Christ.?
圣诞节无疑是一个宗教节日。它是为了庆祝耶稣的诞生。
In fact, there’s no mention of December 25th in the Bible. Early Christians couldn’t even agree on which day Jesus was actually born. It was only in the 3rd century that December 25th became the official celebration of the birth of Jesus. Most likely because it coincided with already existing Pagan festivals.?
其实，圣经上是并没有提到过12月25号这个日子的。早年的基督教徒们也一直对基督具体出生的日子争论不休最终也没有个确切的结果。一直到公元3世纪，才把12月25日定为官方的庆祝耶稣诞生的日子。很可能是和当时已经存在的一些异教徒节的日期有关。
A Christmas tree can be found in most British homes throughout the month of December. In the earliest history of Scandinavia, it was traditional during the celebration of the Winter Solstice (December 21st) to bring an evergreen tree into the home and decorate it. Since the evergreen was the only type of tree that lived through the entire winter, the families saw it as a symbol of continued life.?
大部分英国的家庭都会在12月份在家放一棵圣诞树。最初起源于斯堪的纳维亚，那里的人为了庆祝冬至，会带一棵常青树回家并且装饰它。因为常青树是唯一一种能存活过一整个冬季的树，所以他们把它看成是生命延续的象征。