What is the X in X-mas?
1570s, from Medieval Latin aorta, from Greek aorte, term applied by Aristotle to the great artery of the heart, literally "what is hung up," from aeirein "to lift, heave, raise," of uncertain origin; related to the second element in meteor. Used earlier by Hippocrates of the bronchial tubes. Related: Aortal; aortic.
aorta a·or·ta (ā-ôr'tə)
n. pl. a·or·tas or a·or·tae (-tē)
The large artery that is the main trunk of the systemic arterial system, arising from the base of the left ventricle, ending at the left side of the body of the fourth lumbar vertebra, dividing to form the right and left common iliac arteries, and whose parts are the ascending aorta, the aortic arch, and the descending aorta.