NOX is actually the Latin word for night. In this case it refers to the dark colour scheme of the deck.
When this project was originally concepted there was a light version and a dark version of the deck design. I wanted a unique name that would represent each design, and so NOX and LUX were chosen for the dark and light versions of the deck respectively. The dark version was the clear favourite with everyone I showed the early concepts to, so I decided to lead the project with the NOX deck.
While I would still like to produce the LUX deck at some point, it may be a while before it ever sees the ... light... of day. See what I did there? Ugh... I'm going to bed.