According to the 1899 "Transactions of the Philological Society," noggin is ultimately derived from the obsolete English word knag. Knag morphed into nog and has a couple of meanings that are interesting to explore. First off, it's another word for cask or keg which, like noggins, are wooden vessels for holding liquids. It's also a knot on a tree. If you're wondering what the connection is between tree knots and wooden cups, according to a 1915 article from Boys Life, you saw off the knot of a tree and hollow out the inside until you have a suitable cup.
The "nog" that meant a knot of a tree also came to mean any peg or pin on which to hang something (via The English Dialect Dictionary). Pins were once heated and used to warm alcoholic drinks, drinks that came to be known as nog. According to Dictionaries of the Scots Language, "to nugg" a drink is to heat it in this manner. Over time, people decided to put eggs, sugar, and milk into their nog and now people drink eggnog every Christmas (via Why Christmas?).
ncG1vNJzZmivp6x7qL7Up56eZpOkunCEkGppcXBfnby4ecOim2asmJp6qbHAnWSgnaRiwamxjKegnKOelrqmec2onqChnmQ%3D