From the Gauls to Odilon de Cluny

For the Gauls, the Samain Feast was the most important of their religious events. Everyone in the village took part. Pork, the meat that was generally eaten, was replaced by that from two white bulls sacrificed with their horns tied together after the mistletoe had been collected. People drank beer, wine, and mead ... The feast continued for a week to a fortnight. To frighten away the strange and evil spirits who came out at the time, the Gauls blackened their faces and dressed up in the most terrifying way possible.

Some centuries later, the Catholic Church incorporated the feast into its calendar. In the 8th C, Pope Gregory the Third changed the date of the Feast of the Saints to November. Around 840 AD, Gregory the Fourth created All Saints Day, ordering that both the day and its eve be considered holy days. In 1048, Odilon de Cluny chose November the 2nd as the Day of the Dead.

The English word dates from this period: Allhallows (all who are holy or sacred) Day for the French Toussaint (All Saints), and Allhallows Eve or All Hallow Even for the holy night preceding the Saint's Day; over the centuries this gradually became Hallowe'en and then Halloween.

For more information : "Secrets et mystères d'Halloween"
édition Jacques Grancher, Paris, France