Nittel Nacht

It's customary to refrain from Torah study on X-mas eve (Dec. 24) from sundown until midnight. This period of time is called Nittel Nacht (Yiddish for night).

There are a number of theories as to where the term "Nittel" or "Nittel Nacht" originates.

1. From Judæo-German word for "Christmas"; derived from the medieval Latin "Natale Domini" meaning, "The birth of our God" or from the Latin "Dies Natalis", and French "Noël"

2. From the Hebrew "natal", meaning "to have been hanged".

3. From the Hebrew for "being taken away".

4. An acronym for "Nolad Yeshu Tet L'tevet", meaning, "J. was born on the ninth of Tevet."

The latter interpretations support a theory that J. was killed on Christmas. It may also be a derogatory nickname that was used to refer to J. It was customary to play cards on Nittel night in opposition to the solemn celebration of that evening by Christians, while really it was merely a survival of the old German custom of merrymaking at this festival. It's also customary to play chess or write letters on that night.

We don't learn on nittel nacht (Dec. 24 at night, X-mas eve) in order not to increase vitality [to kelipa].