circulator (n.)

1540s as a chemical term in reference to alternating vaporization and condensation, from Latin circulatus, past participle of circulare "to form a circle," from circulus "small ring" (see circle (n.)).

Intransitive sense of "to pass about freely, pass from place to place or person to person" is from 1660s; of newspapers from 1885. Of blood, "to flow in a continuous circuit," from 1650s; of persons, "to mingle in a social gathering," from 1863. Related: Circulated; circulating.