c. 1300, "figure of a circle, a plane figure whose periphery is everywhere equidistant from its center point," from Old French cercle "circle, ring (for the finger); hoop of a helmet or barrel" (12c.), from Latin circulus "circular figure; small ring, hoop; circular orbit" (also source of Italian cerchio), diminutive of circus "ring" (see circus).
Replaced Old English trendel and hring. Late Old English used circul, from Latin, but only in an astronomical sense. Also used of things felt to be analogous to a circle: The meaning "group of persons surrounding a center of interest" is from 1714 (it also was a secondary sense of Latin circulus); that of "coterie" is from 1640s (a sense also found in Latin circulus).
To come full circle is in Shakespeare. Sense in logic, "inconclusive argument in which unproved statements are used to prove each other" is from 1640s. Meaning "dark mark around or beneath the eyes" is from 1848.
late 14c., cerclen, "to shape like a globe," also "to encompass or surround with a circle," from circle (n.). From c. 1400 as "to set in a circular pattern;" mid-15c. as "to move round in a circle." Related: Circled; circling. To circle the wagons, figuratively, "assume an alert defensive stance" is from 1969, from old Western movies.
"a small circle," late 15c., from French cerclet, diminutive of cercle (see circle (n.)).
"moving through a circuit," c. 1600, of blood, from French circulatoire or directly from Latin circulatorius, from circulator, agent noun from circulare "form a circle," from circulus (see circle (n.)). Circulatory system is recorded from 1862.
1550s in astronomy, in reference to a celestial circle, a line around the sky which, in any location, bounds the stars which are ever-visible from that latitude (in the Northern Hemisphere its center point is the celestial north pole); the concept goes back to the ancient Greeks, for whom this set of constellations included most prominently the two bears (arktoi), hence the name for the circle (see arctic). In Middle English it was the north cercle (late 14c.).
In geography, from 1620s as "the circle roughly 66 degrees 32 minutes north of the equator" (based on obliquity of the ecliptic of 23 degrees 28 minutes), marking the southern extremity of the polar day, when the sun at least theoretically passes the north point without setting on at least one summer day and does not rise on at least one winter one.
late 14c., "round, having the form of a circle," from Anglo-French circuler, Old French circuler "circular" (14c., Modern French circulaire), from Latin circularis, from circulus "small ring" (see circle (n.)). Meaning "intended for circulation" is from 1650s. The metaphoric circular firing squad is attested by 1990.