Halloween 101

Introduction
Halloween is a largely secular celebration on the 31st of October that includes activities such as costume parties and trick or treating . It had its origins  in the Celtic festival of  Samhain  and the Christian holiday All Saint's Day.

Where the word "Halloween" comes from ? 
The word Halloween is believed to appear for first time in the  16th century and represents a Scottish variant of the fuller All-Hallows-Even ("evening"), which is, the night before All Hallows Day.


Why people wear costumes that day?
The ancient Celts believed that the border between this world and the world of the dead became thin on Samhain (end of summer celebration) , allowing spirits (both harmless and harmful) to pass through. The family's ancestors were honoured and invited home while harmful spirits were warded off. It is believed that the need to ward off harmful spirits led to the wearing of costumes and masks. Nowadays, Halloween is a largely secular celebration where adults unleash their inner child to indulge in a little make-believe by wearing fancy dresses

Origin of Trick or Treat?
It originated in Ireland and England when poor folk would go door to door on Hallowmas  on  November 1, receiving food in return for prayers for the dead on All Souls Day. Nowadays, it is just about the candy , children go in costume from house to house, asking for treats (ie: candy), with the question, "Trick or treat?" The word "trick"  to perform mischief on the homeowners or their property if no treat is given.

Source: Wikipedia