Milk or cream, sugar, whipped eggs, and alcohol all go into the making of eggnog, which is a stirred custard-like drink now tied to the holidays. It has been around in one form or another for almost a millennium. According to TIME, eggnog most likely evolved from posset, a heated milk and spice drink similar to ale in medieval Britain. Thirteenth-century monks included eggs and figs in their version of posset, and people also toasted to good fortune and health with the drink.
In the 1700s, the drink took off in America, where the cheap and plentiful rum there made it into the recipe. Easy access to milk and eggs due to the high number of cows and chickens also made eggnog’s popularity surge. Even George Washington was a proponent of the drink, according to CNN. He made it with three different types of alcohol: rum, rye whiskey, and sherry.
Today, eggnog around the world varies by country. Mexico’s version is called the “rompope,” while Puerto Rico’s is the “coquito,” which is made with coconut milk.