Hark the Herald Angels Sing

Christmas carols are based on Christian lyrics and relate, in the main, to the Nativity. Christmas carols were introduced in to church services by St Francis of Assisi in the 12th century.
As for the word carols, "carol" is a derivative of the French word caroller, the interpretation of which means dancing around in a circle.
Carol and carols, eventually came to mean not only to dance but included music and lyrics - hence Christmas Caroling.
 The joyous themes for many traditional Christmas carols were banned in England by the staunch Protestant Oliver Cromwell and many of the very old Christmas carols and songs were subsequently lost for all time.
Christmas carols were only fully popularised again during the Victorian era when they again expressed joyful and merry themes in their carol lyrics as opposed to the normal, more sombre, Christian lyrics found in hymns.
As religious observances in the United States and England were closely linked the popularity of Christmas carols grew in both countries in the 19th century.
Many Christmas traditions are relatively recent such as Santa Claus and reindeer and bear no relation to Christmas carols.
We have reflected this in the unusual and beautiful Victorian Angel Pictures we have included for your pleasure and enjoyment.
Today Christmas songs and carols are also fast becoming a tradition.     
 Merry Christmas and enjoy singing the wonderful words and lyrics to the Christmas carols and Christmas songs:

Carol of the Bells
Angels from the Realms of Glory
Ave Maria
Away in a Manger carol
Christians Awake salute the Happy Morn
Deck the Halls carol
Ding Dong Merrily on High
God Rest Ye Merry Gentlemen
Good Christian Men Rejoice
Good King Wenceslas carol
Hark the Herald Angels Sing
I Saw Three Ships carol
It Came Upon the Midnight Clear
 Christmas Sheet Music
Joy to the World
O Christmas Tree carol
O Come All Ye Faithful
O Come O Come Emmanuel
O Little Town of Bethlehem
Once in Royal Davids City
Silent Night carol
The First Noel carol
The Holly and the Ivy
The Wassail Song
We Three Kings of Orient are
While Shepherds Watched

Source: http://www.carols.org.uk