For the last few millennia, Celtic peoples have marked the changing of the seasons with festivals, including some with terrifying costumes.
The commercialization of Halloween is well-known, with expensive dress-ups, trick-or-treat "candy", and fake cobwebs.
However, Halloween is not an American invention, but rather has its roots in ancient Celtic festivals, such as Samhain, celebrated by Irish and Scottish Gaels at the onset of winter.
Samhain (pronounced "sah-win")
was a time when the harvest would be over, the last livestock would be brought back from summer pastures, and people would prepare for winter, typically around the end of October in the northern hemisphere.
Author's summary: Ancient Celtic festival Samhain marks the start of winter.