The vagus nerve (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired cranial nerves, and is the only nerve that starts in the brainstem (within the medulla oblongata) and extends, through the jugular foramen, down below the head, to the neck, chest and abdomen.
The medieval Latin word vagus means literally "Wandering" (the words vagrant, vagabond, and vague come from the same root). It is also called the pneumogastric nerve since it innervates both the lungs and the stomach.