‘Circulation’ is not only among the most widely used words in the language of global history; it is also among the most erratically employed. Amorphous in its usages and protean in its semantics, ‘circulation’ has come to describe any sort of movement: from circular movement and passage along the vessels of closed systems to, paradoxically, open-ended, unidirectional dissemination. This article asks how ‘circulation’ became prominent metaphorically in global history; it seeks to understand the word’s appeal and the consequences of its ascendancy. It argues that the popularity of ‘circulation’ is attributable to a merger of two of its qualities: its seeming ‘untainted-ness’ and openness, on the one hand, and on the other, how its older, medical and economic, meanings resonate in its usages, allowing it to convey a sense of entity (independent existence) for the terrain in which ‘circulation’ occurs, and a sense of directedness, self-reliance, and ‘liquidity’ for the movements it describes.