Which Christmas song is thought to have been written for a Thanksgiving Sunday School Program?

The song "Jingle Bells" is thought to have been written for a Thanksgiving Sunday School Program. Jingle Bells was originally called One Horse Open Sleigh and was written by James Pierpont sometime between 1853 and 1857. He composed One Horse Open Sleigh, reportedly for a Thanksgiving program.

He later publicly released the song through Ditson and Co. of Boston in 1857, but it wasn't terribly popular. Pierpont tried again to release it in 1859 under the new title Jingle Bells, with it once again flopping. However, from there, it did slowly gain in popularity and became associated with Christmas, rather than just as a general sleigh-song, which were a popular type of song at the time among teenagers.

By 1890, three years before Pierpont's death, the song had become a huge Christmas hit and from 1890 to 1954 it managed to maintain a spot on the top 25 most recorded songs in the world.