1. The less movable of the two points of attachment of a muscle, that which is attached to the more fixed part of the skeleton. 2. The starting point of a cranial or spinal nerve. The former have two origins: the ental origin, deep origin, or real origin, the cell group in the brain or medulla, from which the fibers of the nerve begin, and the ectal origin, superficial origin, or apparent origin, the point where the nerve emerges from the brain.