For millennia, Celtic peoples have marked the changing of seasons with festivals, including some with terrifying costumes.
Halloween has become commercialized with expensive costumes, trick-or-treat candy, and fake cobwebs.
However, Halloween is not an American invention, but rather has its roots in Celtic festivals, such as Samhain, celebrated by Irish and Scottish Gaels at the onset of winter.
For at least the past couple of millennia, the changing of the seasons has been marked among Celtic peoples with festivals at recognised times of year.
Samhain, pronounced "sah-win", was celebrated around the end of October in the northern hemisphere, marking the end of the harvest, the return of livestock from summer pastures, and preparation for winter.
Author's summary: Samhain is the Celtic origin of Halloween.