I wubbs teh interwebs
Once upon a time, I could ponder a question like "I know what egg nog is, but what th' heck is 'Nog'?" for weeks, but now I can just use a little Google-Fu and discover:
The origins, etymology, and even the ingredients used to make the original eggnog drink are debated. Eggnog, or a very similar drink, may have originated in East Anglia, England, though it may also have been developed from posset (a medieval European beverage made with hot milk). An article by Nanna Rögnvaldsdóttir, an Icelandic food expert, states that the drink adopted the "nog" part of its name from the word "noggin", a Middle English term used to describe a small, wooden, carved mug used to serve alcohol. Another name for this British drink was Egg Flip. Yet another story is that the term derived from the name "egg-and-grog", a common Colonial term used to describe rum. Eventually the term was shortened to "egg'n'grog", then "eggnog".
From http://en.wikipedia.org/wiki/Egg_nog
The origins, etymology, and even the ingredients used to make the original eggnog drink are debated. Eggnog, or a very similar drink, may have originated in East Anglia, England, though it may also have been developed from posset (a medieval European beverage made with hot milk). An article by Nanna Rögnvaldsdóttir, an Icelandic food expert, states that the drink adopted the "nog" part of its name from the word "noggin", a Middle English term used to describe a small, wooden, carved mug used to serve alcohol. Another name for this British drink was Egg Flip. Yet another story is that the term derived from the name "egg-and-grog", a common Colonial term used to describe rum. Eventually the term was shortened to "egg'n'grog", then "eggnog".
From http://en.wikipedia.org/wiki/Egg_nog