Literally means 'the mind with no remainder' or in other words the state of complete awareness. Awareness of the body, mind and the surroundings in total ease. It is about acting in purpose and intention with pure intensity but not bothered or stressed out about the result. It is about being totally fired up but in utter ease.
The purpose of this name is that whoever holds these knives and sees this kanji is for them to be reminded of this state of awareness.