mid-15c., circulacioun, in alchemy, "process of changing something from one element into another," 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.)).

Of blood, "act of moving so that it returns and begins again," first by William Harvey, 1620s. Meaning "act or state of being distributed" is from 1680s; that of "extent to which a thing circulates" (of periodical publications) is from 1847.

1794, "pertaining to or moving in a cycle or circle," from French cyclique (16c.), from Latin cyclicus, from Greek kyklikos "moving in a circle," from kyklos "circle, wheel, any circular body, circular motion, cycle of events" (see cycle (n.)). Sense of "connected to a literary cycle" is by 1822.

symbolic magic circle used by Buddhists in meditation, 1859, from Sanskrit mandala "disc, circle." Adopted 20c. in Jungian psychology as a symbol of unity of the self and completeness.

1848, "extensive storm characterized by the revolution of air around a calm center in which the wind blows spirally around the center," coined by British East India Company official Henry Piddington to describe the devastating storm of December 1789 in Coringa, India; irregularly formed from a Latinized form of Greek kyklon "moving in a circle, whirling around," present participle of kykloun "move in a circle, whirl," from kyklos "circle" (from PIE root *kwel- (1) "revolve, move round"). Applied to tornadoes from 1856.

"exclusive set or circle of persons who are in the habit of meeting and socializing, a clique," 1738, from French coterie "circle of acquaintances," originally an organization of peasants holding land from a feudal lord (14c.), from cotier "tenant of a cote" (see cottage).