Where did the tradition come from??

The tradition originated with the ancient Celtic festival of Samhain, when people would light bonfires and wear costumes to ward of ghosts. In the eighth century, Pope Gregory III designated November 1 as All Saints Day a time to honor all saints.

November 2 is All Souls’ Day in honor of all the dead who passed the previous year releasing their souls to go to their next destination. All Souls’ Day was celebrated similarly to Samhain, with big bonfires, parades and dressing up in costumes as saints, angels and devils.

The All Saints’ Day celebration was also called All-hallows or All-hallowmas (from Mid English meaning All Saints’ Day).

The night before All Saints’ Day, the traditional night of Samhain in the Celtic religion began to be called All-Hallows Eve and eventually, Halloween, according to History.com.