Comes from the english word "Schizophrenia," which is derived from the latin terms "Schiz" (Split) and Phren (Mind). Since the introduction of the electromagnetic spectrum, we humans have learned that what we can touch, smell, see, and hear with our 5 senses makes up less than one millionth of reality. Therefore, we do not know what makes up the rest of reality and how that counteracts or balances out the reality of which we know. This means that the rest of reality may cancel out or build upon the reality of which we all know, thus creating the possibility that it doesn't exist at all.
The term "Schitz" is used abstractly and as a paradox because, since we do not know what makes up reality and its effects on the reality humans can sense, the closest one can get to explaining it all is in a paradoxical form. It is and it isn't.
Person 1: "Schitz..."
Person 1+2: "But not at all."