ἀρτηρία

Artēría in Greek comes from aer (air) and terein (to keep or contain) — an air-container. When Greek physicians dissected cadavers, they found the arteries empty. Blood pools in the veins after death because arterial pressure pushes blood out of the arteries and into the venous system. The Greeks looked at the empty tubes and concluded, logically but incorrectly, that arteries carried air. The windpipe was also called an arteria — arteria tracheia (rough air tube) — because it genuinely does carry air.

Galen of Pergamon, in the second century CE, corrected the error. He demonstrated through vivisection (live animal dissection) that arteries carry blood, not air. The blood in arteries is bright red and under pressure — it spurts when an artery is cut. Galen showed this repeatedly. But the name 'artery' was already fixed. The word that means 'air tube' has meant 'blood tube' for two thousand years.

The word acquired a figurative meaning by the eighteenth century. An artery was any main route of flow — traffic arteries, arterial roads, the arteries of commerce. The metaphor is physical: just as arteries carry blood from the heart to the body's extremities, arterial roads carry traffic from the center of a city to its outskirts. The word saw the branching pattern and borrowed it.

Arterial disease — atherosclerosis, the hardening and narrowing of arteries — is the leading cause of death worldwide. The arteries that the Greeks thought carried air are now the focus of the largest branch of modern medicine. Coronary artery disease, peripheral artery disease, carotid artery stenosis — the Greek air tubes turned out to be the most consequential tubes in the body.