The word "carol" comes from the Greek choraulien which means dancing (choros) and playing the flute (aulien). In other words, the carol was a dance to flute accompaniment. In ancient times, this kind of dancing was extremely popular with the Greeks and Romans.
In the Middle Ages in England and France, carols were dances accompanied by singing. In the French Midi, for example, the "carol" was a kind of round dance. In time, the word "carol" changed its meaning, referring only to certain kinds of songs. The Anglo-Saxon tradition favoured gathering together small choirs on the village green to sing carols and Christmas songs for the pleasure of passers-by. A number of currently very popular American Christmas carols come directly from France and England.