In Austria some people leave bread, water and a lighted lamp on the table before going to bed. It is believed that this will welcome dead souls back to Earth.
Gaels believed that it was a time when the walls between our world and the next became thin and porous, allowing spirits to pass through, come back to life on the day and damage their crops. Places were set at the dinner table to appease and welcome the spirits.
The phrase trick-or-treat was first used in America in 1927, with the traditions brought over to America by immigrants. Guising gave way to threatening pranks in exchange for sweets.