1. Itisness comes from itis which means being sleepy typically as a result of eating a large fatty meal. Itisness extends this to mean a state of relaxation or idleness.
2. Itisness was read as it-is-ness and so was interpreted as meaning a meditative state of being which is ironically similar to the original meaning. It is also used as a one word explanation for anything.
1. Sundays are my days of itisness, sitting on the couch watching talk shows.
2. I tried to find reasons why, but failed and had to settle for itisness.