The holiday of Halloween originally comes from the approximate area that is now Ireland, where there was a group of people called the Celts who lived there about 2,000 years ago. When October ended and November began, the Celts held a festival to mark the end of summer and the gathering of their harvest for winter! During this festival (known then as Samhain), on the night of October 31st, the Celts believed that ghosts would come around and haunt people for the night! In order to scare the ghosts away, it became tradition to dress up like other things that would fool the ghosts and bad spirits!
Later, when the region occupied by the Celts was conquered by the Romans, two Roman festivals (that respectively commemorated the passing of the dead and honored the goddess of the harvest) were combined with the Celtic festival of Samhain. Then, in the seventh century, Pope Boniface IV declared that November 1st would be All Saints’ Day, also known as All-hallows Day. While many people think he did this to try and change the focus of the preceding night’s festival, it is also where modern-day Halloween gets its name: The night before All-hallows Day became known as All-hallow’s Eve, and eventually “Halloween”!
Over time, as observances and traditions changed, Halloween went from being a Celtic harvest festival to the trick-or-treating holiday we know today! Lots of people still celebrate Halloween by dressing up in costume, and the holiday has moved from its original region and is now celebrated in many countries all over the world! While some people chose not to celebrate it because it is not a holiday that comes from their religion or culture, others have adapted it and celebrate anyway!