It may not be as popular as "Rudolph, the Red-Nosed Reindeer," but “I Heard the Bells on Christmas Day” is a holiday classic. In case you need a refresher, here’s Bing Crosby’s rendition:

Nearly 10 years before it was a song, the composition was a Henry Wadsworth Longfellow poem called “Christmas Bells.” It had been a tough couple of years for Longfellow. In 1861, his wife suffered a terrible death right in front of his eyes. Fanny Longfellow had been trimming their 7-year-old daughter’s hair and decided to preserve some of the curls in sealing wax. Something went wrong during the process—some say a gust of wind blew the hot wax onto her dress, while others blame a self-lighting match—and Fanny's dress went up in flames. She ran into her husband’s study for help; he burned himself badly trying to put her out. But his efforts were for naught; she died the next morning and he was too injured to attend her funeral.

In 1863, their 17-year-old son, Charles Appleton Longfellow, ran away to enlist in the Union Army. He left his father a note, explaining, "You know for how a long time I have been wanting to go to war I have tried hard to resist the temptation of going without your leave but I cannot any longer, I feel it to be my first duty to do what I can for my country and I would willingly lay down my life for it if it would be of any good God Bless you all."

The commanding officer knew the family and contacted the elder Longfellow, who gave his consent despite being very much against it. Charley hadn’t been in the service long when he contracted malaria and typhoid fever and had to come home to recover. Though he was gravely ill, the diseases turned out to be a blessing in disguise: While he was at home getting well, Charley missed the Battle of Gettysburg, which killed or wounded more than 51,000 soldiers. Charley returned to his post in August, and on December 1, his father received devastating news: His young son had been shot during the Battle of Mine Run on November 27, with a bullet clipping his spine. Surgeons warned the family that Charles may never walk again.

Amazingly, Charley made a full recovery. But when Longfellow put pen to paper to write “Christmas Bells,” he definitely had the horrors of the Civil War on his mind. Composer John Baptiste Calkin put the words to music in 1872, but when you hear the song performed these days, the two verses that obviously refer to the War Between the States are usually left out:

Then from each black, accursed mouth
The cannon thundered in the South,
And with the sound
The carols drowned
Of peace on earth, good-will to men!

It was as if an earthquake rent
The hearth-stones of a continent,
And made forlorn
The households born
Of peace on earth, good-will to men!