Halloween originated as a Pagan celebration called the festival of Samhain, an ancient Celtic tradition commemorating the harvest at the end of the summer months.
Samhain (meaning “summer’s end”) was said to be a god of death. Departed ones were resurrected by Samhain when the veil between the worlds of the living and death was most thin, i.e. the festival.
Participants of said event would dress up in costumes to ward off ghosts; However, during the eighth century, the Catholic pope, Pope Gregory III, adopted the holiday and rebranded it as “All Saints Day.” All Saints Day was a holiday meant to commemorate saints, preceded by “All Hallows Eve” on October 31st. During All Hallows Eve, mischievous spirits were rumored to walk among us and cause trouble for the living.
Following the potato famine in Ireland, the primarily Catholic Irish population continued to practice the traditions of All Saints Day and All Hallows Eve and, as America progressed as a country, they were eventually assimilated into various cultures and heritages. Eventually, they became the commercialized version of Halloween we know today!