Halloween orignated in Ireland around 2000 years ago. It oringanted from the ancient Celtic Festival of Samhain. The Celtic Festival of Samhain the Gods played tricks on their mortal worshipers and even sacrifices were made.
When is it celeberated
It is celebrated on October 31st. Novemeber 1st was when they celebrated the end of the harvest
Traditions
Some of their traditions are:
They carve radishes and turnips to frighten Jack's wandering soul. Hence the term Jack O' Latern
The tradition originated with the ancient Celtic festival of Samhain. The Celtics believed they could not prevail over the troubles of the season or the activities of the deities
People would light bonfires and wear costumes to ward off ghosts.
More Information
Here are some of the websites I used to gather this information
This website I used for general information about what they do for Halloween. History.com
This website I used for information about the Celtic Festival of Samhain Britannica.com