Etymologically, pardon means "to be forgiven" and "asking for forgiveness". This term, today associated with Brittany, had a few echoes in the Middle Ages outside this region, and none after that period. The word could, however, be found, "un-Bretonised", in the first Breton-French dictionary dating from 1499, the Catholicon. It gradually took on its current meaning: a solemn, collective pilgrimage accompanied by an indulgence.

The pardon is the fruit of various phenomenons:
- Celtic forms of worship attested before Romanisation.
- Emigration in the 6th and 7th centuries which brought the worship of several local saints.
The appearance of sanctuaries linked to the miraculous water of a fountain, the power of a menhir, or the particular favour of a civil or religious person.

A few pardons developed at the same time as the Tro Breiz, a unique and major pilgrimage during the Middle Ages in Brittany which brought pilgrims to the tombs of seven founding saints. The Tro Breiz is the only pilgrimage that can rival those of Jerusalem, Chartres or Rome. The pilgrimage spans Brittany, 15 to 20 km per day for a total of 548 kilometers in four to five weeks which take the pilgrims to the tombs of the seven founding bishops from the British Isles: Corentin at Quimper, Pol-Aurélien at Saint-Pol-de-Léon, Tugdual at Tréguier, Brieuc in Saint-Brieuc, Malo in Saint-Malo, Samson in Dol and Patern in Vannes. Any Breton who did the Tro Breiz was sure to go to Paradise; any who failed to do it during his lifetime was condemned after his death to carry it out by advancing the length of his coffin every seven years.

Encouraged in the 17th and 18th centuries by missionary activism, taking strength from events which set an example for all of Brittany such as the founding of the Sainte-Anne-d'Auray pilgrimage, pardons set themselves apart with the indulgences obtained, the miracles which were said to take place, and the zeal of the religious figures seeking offerings. Jacques Cambry, a missionary for the Convention, wrote: "In Brittany the word pardon refers to a chapel, a fountain, a site preserved by the memory of a few saints or a miracle. People come to confess, to take communion, to give to charity, to submit to some superstitious practice, to buy crosses, rosaries and images that they touch to the statue of the half-god; they rub their knees, their foreheads, their paralysed arms against a mystical rock; they throw farthings and pins into the fountains, they wet their shirts to be healed, their belts to give birth easily, their children to make them immune to pain. They dance and leave intoxicated, emptied of money but full of hope. Don't you find in these superstitious practices a less civilised era?"

Despite the clergy's efforts to restrict the profane aspects of the pardon, to fight against abuses and renew faith, pardons had a golden age in the mid-19th century, marked by several crownings of Notre Dame and the creation of sanctuaries which could host several thousand pilgrims. Artists and tourists gradually joined the crowd to admire the traditional costumes and watch these original practices. Pardons fell out of favour in the 20th century — many were destroyed or turned into fun fairs. Towards the end of the century, though, the pardon was revived at the initiative of local associations — a personal and spontaneous movement on the part of Bretons who, in search of their roots, are recreating the Tro Breiz, which had been forgotten for centuries.