The Collaborative International Dictionary of English v.0.48:

Nog \Nog\, n. [Abbrev. fr. noggin.]
   1. A noggin.
      [1913 Webster]

   2. A kind of strong ale. --Halliwell.
      [1913 Webster]

   3. eggnog.
      [PJC]

   egg nog A drink make from eggs beaten with milk, cream, and
      sugar, often spiked with rum or other alcoholic liquor,
      and sometimes seasoned with cinnamon; usually spelled
      eggnog. It is a traditional drink served at social
      gatherings during the Christmas season.
      [PJC]