From the FAQ of the old site:
"Caissa (kah-EE-suh) is the ""patron goddess"" of chess players."
 
However, the video tutorials are pronouncing it variously as "KAY-sa" or "KEE-sa". What gives?

The correct pronunciation is kah-EE-suh. When I listen to myself on the videos I seem to be pronouncing it that way. However in my rush to pack in as much narration as possible I may end up saying something closer to KEE-sa. I suppose the discrepancy could also be due to the quality of Internet audio, sound cards, speakers, etc.