Hallowen

The idea of halloween originally came from the religious practises of the romans and druids. They worshipped various gods and eventually began honouring a lord of the dead, in a feast on October 31. They believed that on the night before November 1, Samhain (the lord of the dead) called together wicked spirits and souls that lived in animal bodies. They believed that the day was surrounded by elves, witches, fairies, etc. So they thought they had to sacrifice their gods in order to protect themselves from these things.

However, the idea of trick-or-treating and jack-o-lanterns came from Ireland. The carved pumpkin was a symbol of an irish damned soul. Trick-or-treating was when poor irish farmers would go door to door begging for food and threatening if they didn't treat them they would trick them in revenge.

Later on during the middle ages when the roman church became more prodestant, they decided to celebrate some pagen feasts. First it was call "Alhallowmass" but then since it was during the evening it changed to "All Halloweed Evening", and of course overtime shortend to "Halloween".