Short answers, pulled from the story.
The Christian Church established All Hallows' Day on the 1st of November to honor all saints and martyrs. Pope Boniface IV re-dedicated the Pantheon in Rome to St Mary and all martyrs by the 4th century. This created a liturgical period known as Allhallowtide that included the vigil of All Hallows' Eve.
The jack-o'-lantern originated from a dark Irish folktale about a man named Stingy Jack who was denied entry to both heaven and hell. He was forced to wander the earth with a burning coal inside a hollowed-out turnip. People in Ireland and Scotland carved grotesque faces into turnips, mangel wurzels, and potatoes to ward off evil spirits in the 16th century.
The term trick-or-treat appeared in print as early as 1917 in The Sault Daily Star. The practice of children going house-to-house in costume, known as guising, was first recorded in North America in 1911 in Kingston, Ontario. By the 1930s, the custom had become widespread and transformed from a rural folk tradition into a national phenomenon.
The Trunk-or-Treat program was established in 1950 to support UNICEF and has since raised over $118 million for children's charities. The holiday's commercialization accelerated in the 20th century with the first recorded use of the phrase trick-or-treat appearing in national publications in 1939. Projections for 2023 reached $12.2 billion in annual spending.
Unmarried women in Ireland and Scotland gazed into a mirror in a darkened room to see the face of their future husband. Others played púicíní, a game where blindfolded participants chose between saucers containing items like rings, coins, or rosary beads to predict their destiny. These games were deeply rooted in Celtic mythology where apples were associated with the Otherworld and hazelnuts with divine wisdom.