Eggnog (or egg nog) is a type of milk-based punch belonging to the posset family. It originates in Europe and its name may have originated from grog or from a small drinking cup known as a noggin. Eggnog typically consists of milk, eggs, and sugar mixed together and may be served with or without added spirits. Other ingredients include spices such as nutmeg, cinnamon, or allspice. Eggnog is typically served as a Christmas time drink. Although rarely as good as "homemade" recipes, ready-made eggnog containing alcohol and "just-add-alcohol" versions are available for purchase in a variety of stores.
Nog is an old English dialect word (from East Anglia) of obscure origins that was used to describe a kind of strong beer (hence noggin).
Those who could get milk and eggs to make eggnog mixed it with brandy or Madeira or even sherry." But it became most popular in America, where farms and dairy products were plentiful, as was rum.
The recipe for eggnog (eggs beaten with sugar, milk or cream, and some kind of spirit) has traveled well, adapting to local tastes wherever it has landed.