1. The origins of Halloween date back to the ancient Celts, who lived over 2,000 years ago.

2. The ancient Celt’s celebrated their new year on November 1, which marked the beginning of a time of year associated with human death. They believed the spirits would return to earth, damaging their crops and causing trouble.

3. Druidic Celt’s would build giant bonfires, where they would burn crops and animals as sacrifices. They would wear animal heads and skins as costumes. Costumes were used to change the persona of the wearer so they could communicate with the spirit world, often to scare off evil spirits.

4. For the people who were afraid of the ghosts, they would wear costumes to avoid being recognized by them.

5. People would place bowls of food and treats outside their houses to prevent the ghosts from entering their homes.

6. Trick or treating comes from the idea that ghosts would cause trouble on Halloween nights. People soon realized they could get away with shit by blaming it on the ghosts and witches, hence the “tricking”.

7. Going door to door for treats originated from the Druidic practice of begging for wood for the great bonfires. It can also be traced back to a Catholic custom of begging for a “soul cake”, where people would go door to door offering prayers for the death in exchange for treats like “soul cakes”.

8. “Trick or treating” didn’t come back into tradition until around the 1930s, when Halloween became more popular. Due to the high increase in numbers of children in the 1950’s, vandalism increased and plagued Halloween celebrations. Families would prevent tricks from being played on them by giving the children candy and treats. This brought on the revival of “trick or treating”.

9. The superstition of black cats bringing bad luck comes from the Middle Ages, when people believed witches would transform into cats to avoid being seen.

10. Pope Gregory III designated November 1^st as All Saint’s Day, and the evening before it was known as All Hollow’s Eve (hence the name Halloween).

11. The original jack-o’-lanterns were made out of potatoes, turnips, and beets, which were native to Ireland.

12. In North America, immigrant’s started using pumpkins since they were native to America and easier to carve.

13. Jack O’Lanterns originate from an old Irish tale about a man called “Stingy Jack” who tricked the devil. You can read more about that tale here.

References:

http://www.history.com/topics/halloween/jack-olant...

http://www1.cbn.com/the-pagan-roots-of-halloween

http://www.history.com/topics/halloween/history-of-halloween