Christmas cookies began in medieval times with cookies flavored with Christmas spices, dried fruit and nuts. Cut-out cookies trace back to 18th century England when people used them as props when acting out Christmas stories.
Eggnog is from the British aristocracy who drank the warm milk and egg beverages with expensive spices and brandy to keep it from spoiling.
Gingerbread houses originated in Germany in the 16th century. Popularity rose with the story of Hansel and Gretel, who found a house made entirely of treats. But it is unclear if gingerbread houses were a result of the fairy tale or vice versa.
Popcorn garland began when families created their own Christmas tree decorations. Stringing popcorn began in Europe when trees were decorated with berries, popcorn and nuts to feed the birds during winter.
In medieval Germany, families used apples, wafers and cookies as ornaments. But when edible tree ornaments became less popular, families blamed Santa for snacking on the tasty ornaments. Then, families began to leave a plate of cookies for Santa by the fireplace.
Sources: The Daily Meal and PBS