Chayah · חיה — the living oneחיה

Bereshit Rabbah's reason is the plainest in the list, and it is an observation about death: it is called chayah, living, because the limbs die and this does not.

The Kabbalah raises the name into a level — the border where a person's awareness meets what is above their awareness. It is filed at Chokhmah, the flash before the thought, and in Atzilut, the world of nearness.

⚠ Dating matters here. Chayah is a name in the fifth-century midrash and a rung in the sixteenth-century Lurianic system, and those are different claims. The later tradition often says chayah and yechidah are makkifim — encompassing rather than indwelling, surrounding the person instead of living inside them, which is why they are also called the parts of the soul you cannot introspect your way to. Compare tselem, the garment worn between soul and flesh: the same instinct that some of you is worn rather than contained.