The notion of Halloween started with Samhain, an ancient Gaelic festival that marked the last day of harvest. Gaelic people believed that from sunset on October 31 to sunset on November 1, fairies, nature spirits, and souls of the dead were out and about. There were feasts and bonfires. Some people went door-to-door in disguise and recited verses in exchange for food, usually apples and nuts.
Today little costumed fairies and "walking dead" still go door-to-door. But apples and nuts have been replaced by Kit Kats and Milky Ways.
If you are looking for a fun picture book to read to a special little goblin during this season, you might want to give ROOM ON THE BROOM a try. It's about a witch that keeps adding passengers to her broomstick.