Eggnog is a tradition that arrived in America from Europe although not in its current form.
In Europe there were many milk and wine punches served at festive times however once in America Rum was used as a substitute for wine.
There seems to be a difference of opinion as to how the Colonial American Milk punch became known as Eggnog.
One theory is that as Rum was commonly known as "grog" and the punch contained Egg the name derived from the description of the drink, "egg-and-grog".
This would have been corrupted to egg'n'grog and then eventually to eggnog.
Another theory claims that the "nog" in eggnog stems from the word "noggin". A noggin being a crude small carved wooden mug often used in low taverns.
So if you have an egg drink in a noggin the drink becomes eggnog.
The final theory is a mixture of the previous two and so claims that eggnog was originally called "egg and grog in a noggin".
They all seem equally unconvincing but without a doubt the jury is still out on the last one I think.
Eggnog is still a popular drink during the holidays today and it's hard to imagine a Christmas without a cup of the "Eggnog" to spice up a gathering and lend merriment and joy to the proceedings.