greek roots for psyche meaning pertaining to or of the mind.
T being short for time out.
By saying psyche-t you are essentially letting someone know that due to their incredibly obvious general; being of a tool or a douchebag, you are autonomically putting your psyche (or mind) on time out. In looser terms you are essentially punishing yourself by continuing to listen to them.
Obvious tool: Due to the fact the we both like cheese I propose that we get together for sex and kraft dinner after school.
Myself: Ah. Psyche-T. Waddidisay.
Obvious tool: You see, you're like cheese, 32% fat, 21% moisture, melty, yellow.
Myself: Sigh. If you were a reader of urban dictionary than I would be proving that you're an arrogant obvious tool as well.