"Silent Night" is a traditional Christmas song. My earliest memory of it is from the television show Rin Tin Tin, when the cavalry sang it during an episode that ran, surprisingly, near Christmas. The first performance of Silent Night was on the 25th in 1818 when a choir sang it during Christmas services in the Church of St. Nikolaus in Oberndorf, Austria.
The song quickly became a staple of the Christmas season. During World War I, a war that probably set the standard for brutality in the modern era, on Christmas Day in 1914, the song was sung simultaneously, in English and German, by the troops facing each other near Ypres, Belgium. When they finished singing, the soldiers from both sides exchanged gifts with their adversaries. After gathering, the Germans and the Allies also conducted a group reading of the 23rd psalm. Sadly, after burying their dead it was back to business as usual for both sides. Currently, in Dallas, Texas, the men's chorus of the Turtle Creek Chorale traditionally ends its annual Christmas season concerts by singing the first verse of the carol, and then signing the verse in complete silence.