The origin of the religious celebration on Christmas Eve is not unique, and there are several explanations that perculate. Three hypotheses stand out from the rest.

According to popular belief, the animal that announced the birth of the Infant, before any other in Bethlehem, was a rooster, hence "Missa del Gall" (literally, "Mass of the Rooster"). Its call would have spread the good news far and wide.

Another theory places the custom in Jerusalem. In this city, the faithful attended a night service and then walked through the streets in procession to the main sanctuary. A new service was taking place there just as the rooster crowed.

The last theory takes us to 5th-century Rome. Sixtus III, then Pope, established a prayer vigil that began when the rooster crowed. For the ancient Romans, the day began ad galli cantus, that is, when the rooster crows, a time they associated with twelve o'clock at night.

No matter where you come from, it is a celebration, and that is why, when the service ends, it is customary to invite those present to a hot chocolate or mulled wine accompanied by pastries.

In Andorra, this event takes place in each of the parishes.