1540s (late 15c. as a past participle adjective), as a chemical term for alternating vaporization and condensation, from Latin circulatus, past participle of circulare "to form a circle," from circulus (see circle, n.). Meaning "to move around, revolve" is from 1670s; of blood, from 1650s; of persons, "to mingle in a social gathering," from 1863. Sense of "to pass about freely" is from 1660s; of newspapers from 1885. Related: Circulated; circulating.