[mesmark]

There's a lot of information on google but it originated as a Fall harvest festival/religious event with the Celts.

Trick or treat has several theories but nothing definite.

The Jack o' Lantern comes from a story of an old man Jack who wanders around in purgatory carrying a gourd with a hot coal in it. The coal is from the devil.

I got all of that off the internet a few years ago when I first had to teach Halloween. So, don't take it all as solid fact.