mid-15c., from Middle French circulation or directly from Latin circulationem (nominative circulatio), noun of action from past participle stem of circulare "to form a circle," from circulus "small ring" (see circle (n.)). Used of blood first by William Harvey, 1620s.
circulation cir·cu·la·tion (sûr'kyə-lā'shən)
n.
Movement in a circle or circuit, especially the movement of blood through bodily vessels as a result of the heart's pumping action.