The History of Halloween

Halloween originated in Ireland where it was called Samhain.

Samhain was celebrated among the Celts of Ireland and Great Britain on the day in the Celtic Calendar equivalent to October 31, which was seen as the last day of the light half of the year, after this the dark, cold days of fall and winter would reign until next spring. During that time it was believed that on that particular day of the year, the threshold of winter and darkness, that the boundary between the spirit and flesh worlds became blurred and the dead could pass through to this world. Certain rituals would be performed to allow and encourage friendly spirits to pass over while other rituals served the purpose of keeping malicious ones away. Examples are the lighting of bonfires and Jack O Lanterns carved with frightening faces to scare evil spirits away

The origin of the name Halloween came from the name All Hallows’ (Saints) Eve or Hallows Eve, the day before All Hallows Day which occurred on November 1. It was a day to celebrate the memory of all the saints and martyrs throughout history. With some churches it was seen as an overall commemoration of the dead, coinciding with the date and concept of Samhain.

The customs and traditions associated with Halloween did not reach the US until the immigration of Irish folk to the states during The Great Irish Famine (The Great Hunger).
Communities of Irish folk would gather for their traditional feast and curious natives would eventually adopt the practices themselves.

The tradition of bobbing for apples originated from the belief that apples represented romance or fertility goddesses; the first person to catch an apple would be the next one to get married.
Also it appears that the Jack-o-lantern custom probably comes from Irish folklore. According to the tale a notorious drunkard and trickster named Jack, tricked Satan into climbing a tree. The man then carved the image of a cross in the tree's trunk, trapping the devil up the up it. However, Jack made a deal with the devil saying that if he would never tempt him again, he would promise to let him down the tree.
As the story goes, after Jack died, he was he was not allowed to enter Heaven because of his evil ways nor was he allowed to enter Hell because he had tricked the devil. So instead, the devil gave him a single ember to light his way through the frigid darkness of Nowhere land. The ember was placed inside a hollowed-out turnip to keep it glowing longer.
The Irish originally used turnips as their "Jack's lanterns". But those who immigrated to America found that pumpkins were far more plentiful than turnips. So the Jack-O-Lantern in America was a hollowed-out pumpkin instead.
The practice of trick or treating is of more varied origin. Some say it evolved from the practice of the poor of the neighborhood going from door to door on All Hallows Day and saying prayers for the dead in return for a bit of food in a bag. Others say that it originated from a certain tradition that was seen as very important to the Celts back then. It was generally thought than on that night the spirits of the dead or the fairies, witches, goblins and such would all be roaming around looking for something to eat. These entities were said to have traveled from door to door to collect the offering that the townspeople left on the doorstep for them. To the people of the village, it was very important to leave this offering to ensure that the spirits would not be angered and enter the house to posses a family member. Later children would disguise themselves as some sort of underworld being and beg for a ‘treat’ or else the inhabitants might have to face a ‘trick’.
Halloween is often seen as a cultish worshiping of the dead but it is really a modern form of a age old tradition to ward off the unfriendly dead and honor loved ones who had passed away.
To better understand the traditions behind the holiday is to better appreciate it as a whole.
Now you can brag about your knowledge of the history of the customs behind Halloween.