This chap says it's the Moon after Yule.
http://www.homepages.ucl.ac.uk/~ucapsj0/moon/index.html#tth_13
This is one of the problems with neo-paganism or Reconstructionist paganism.
So much of the history, often passed down from parents to children by word of mouth, writing was only, in the early days, available to the children of the devout (not putting too fine a point on it!) was lost when families lost parents or communities lost their shaman or leader to disease or war and then even more was lost to the arsonist tendencies of the Roman Catholic Church.
These days just about anyone with the ability to read even one of the many "experts" on the subject immediately becomes an expert themselves.
I have spent years on research and there is no way that I would class myself as whatever the lowest classification of expert might be.
There are those who genuinely believe that they are helping others onto or along their chosen path for purely altruistic reasons and there are others, like a certain Christian poster's friend Kevin Carlyon - the King of the British White Witches (the very inclusion of the word "White" in his title tells anyone who knows anything about witches that he is a fraud) who are in it for the money and the adoration of the gullible!
As the advice I got from my first High Priestess put it - if you want to know about Paganism and the Craft read everything that you can get your hands on, take on board those things that feel right to you, then read some more and adjust your path as you learn more, but Rule ONE is that whatever you take on board MUST be what feels right for you and not what feels right for anyone else no matter what title they call themselves by!