Virtually all present Halloween traditions can be traced to the ancient Celtic day of the dead. Halloween is a holiday of many mysterious customs, but each one has a history, or at least a story behind it.
The wearing of costumes, for instance, and roaming from door to door demanding treats can be traced to the Celtic period and the first few centuries of the Christian era, when it was thought that the souls of the dead were out and around, along with fairies, witches, and demons.
Offerings of food and drink were left out to placate them. As the centuries wore on, people began dressing like these dreadful creatures, performing antics in exchange for food and drink. This practice is called ‘mumming, from which the practice of trick-or-treating evolved.
To this day, witches, ghosts, and skeleton figures of the dead are among the favorite disguises. Halloween also retains some features that harken back to the original harvest holiday of 'Samhain, such as the customs of bobbing for apples and carving vegetables, as well as the fruits, nuts, and spices cider associated with the day.