Dashing through the snow
In a one horse open sleigh
O'er the fields we go
Laughing all the way
Bells on bob tails ring
Making spirits bright
What fun it is to laugh and sing
A sleighing song tonight
Oh, jingle bells, jingle bells
Jingle all the way
Oh, what fun it is to ride
In a one horse open sleigh

These days the sound of jingle bells heralds the arrival of Santa Claus and Christmas, with bellows of ho ho hos and a jolly welcome for the many little children who throng around him waiting to tell him what they want for Christmas.
In past eras, jingle bells could be heard down snowy lanes as horse drawn sleighs approached. They were actually there for a practical reason. They served as a warning signal to other sleighs and carriages as they came up to corners or drove through snow. In many areas, they were required by law. Sleighs are much more difficult to stop than wagons so having ample warning of another sleigh or carriage gave time to slow down and stop.
Horse bells go back for centuries in England. Single horse bells, which were called "crotals" adorned war horses in the middle ages and were a sign of wealth and state. People believed that the horse bells would bring good luck and prosperity and protect them from evil and poor health.
Jingle bells became more and more popular for horse drawn sleighs in the 1800s, when sleigh riding and racing became a popular form of winter entertainment. Winter sleigh racing was exciting, the horses manes flying as they sped through the snow. In fact, winter sleigh sports inspired James Pieropont to write the song "Jingle Bells", which was originally called "One Horse Open Sleigh". He taught the new song to his Church choir and published it in 1857.