Online Etymology Dictionary

circular (adj.): late 14c., from Anglo-French circuler, Old French circuler "circular" (14c., Modern French circulaire), from Latin circularis, from circulus (see circle (n.)). The metaphoric circular firing squad is attested by 1990.
circular (n.): 1550s, "circular figure," from circular (adj.). Meaning "a notice circulated" is from 1818.
circularity (n.): 1580s, from circular (adj.) + -ity.
circulate (v.): 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.
circulation (n.): mid-15c., from Middle French circulation or directly 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.)). Used of blood first by William Harvey, 1620s.
circulator (n.): "one who puts (something) in circulation," 1755, agent noun in Latin form from circulate (v.). Classical Latin circulator meant "peddler, hawker," a sense attested occasionally in English 17c. and after.
circulatory (adj.): c. 1600, of blood, from French circulatoire or directly from Latin circulatorius, from circulator, agent noun from circulare (see circulate). Circulatory system is recorded from 1862.
circum-: word-forming element meaning "around, all around, on all sides," from Latin circum- a common element in word-formation, from adverb and preposition circum "around, round about," literally "in a circle," probably accusative form of circus "ring" (see circus). In French, the element became circon-; Kitchin points out that con for cum is common even in classical Latin.
circumambient (adj.): 1630s, from circum- + ambient.
circumambulate (v.): 1650s, from Latin circumambulatus, past participle of circumambulare "to walk around," from circum "around" (see circum-) + ambulare "to walk" (see amble). Related: Circumambulated; circumambulating; circumambulation.
circumcise (v.): mid-13c., "to cut off the foreskin," from Old French circoncisier "circumcise" (12c., Modern French circoncire), from Latin circumcisus, past participle of circumcidere "to cut round, to cut trim, to cut off" (see circumcision). Related: Circumcised; circumcising.
circumcision (n.): late 12c., from Latin circumcisionem (nominative circumcisio), noun of action from past participle stem of circumcidere "to cut around; cut, clip, trim," from circum "around" (see circum-) + caedere "to cut" (see -cide).
circumduction (n.): 1570s, from Latin circumductionem (nominative circumductio), noun of action from past participle stem of circumducere "to lead around, move or drive around," from circum "around" (see circum-) + ducere "to lead" (see duke (n.)). Related: Circumduce.
circumference (n.): late 14c., from Latin circumferentia, neuter plural of circumferens, present participle of circumferre "to lead around, take around, carry around," from circum "around" (see circum-) + ferre "to carry" (see infer). A loan-translation of Greek periphereia "periphery, the line round a circular body," literally "a carrying round" (see periphery). Related: Circumferential.
circumflex (n.): 1570s, from Latin (accentus) circumflexus, "bent around," past participle of circumflectere "to bend around," of a charioteer, "turn around" (from circum "around;" see circum-, + flectere "to bend;" see flexible); used as a loan-translation of Greek (prosodia) perispomenos (Dionysius of Halicarnassus), literally "drawn-around," with reference to shape.
circumfluent (adj.): 1570s, from Latin circumfluentem (nominative circumfluens), present participle of circumfluere "to flow around," from circum- (see circum-) + fluere (see fluent).
circumjacent (adj.): late 15c., from Latin circumiacens, present participle of circumiacere "to border upon, to lie round about, enjoin," from circum- "around" (see circum-) + iacere "to throw, cast, hurl" (see jet (v.)). Related: Circumjacence; circumjacency.
circumlocution (n.): c. 1400, from Latin circumlocutionem (nominative circumlocutio) "a speaking around" (the topic), from circum- "around" (see circum-) + locutionem (nominative locutio) "a speaking," noun of action from past participle stem of loqui "to speak" (see locution). A loan-translation of Greek periphrasis (see periphrasis).
circumnavigate (v.): 1630s, from Latin circumnavigatus, past participle of circumnavigare "to sail round," from circum "around" (see circum-) + navigare (see navigation). Related: Circumnavigated; circumnavigating; circumnavigable.
circumnavigation (n.): 1705, from circumnavigate + -ion.
circumpolar (adj.): 1680s in astronomy; 1690s in geography, from circum- + polar.
circumscribe (v.): late 14c., from Latin circumscribere "to make a circle around, encircle, draw a line around; limit, restrain, confine, set the boundaries of," from circum- "around" (see circum-) + scribere "write" (see script (n.)). Related: Circumscribed; circumscribing.
circumscription (n.): 1530s, from Latin circumscriptionem (nominative circumscriptio) "an encircling; fact of being held to set limits," noun of action from past participle stem of circumscribere (see circumscribe). Figurative sense of "setting limits of meaning" is earliest in English.
circumspect (adj.): early 15c., from Latin circumspectus "deliberate, guarded, well-considered," past participle of circumspicere "look around, take heed," from circum- "around" (see circum-) + specere "to look" (see scope (n.1)). Related: Circumspectly; circumspectness.
circumspection (n.): late 14c., "careful observation of one's surroundings," from Old French circumspection (Modern French circonspection), from Latin circumspectionem (nominative circumspectio) "a looking around; foresight, caution," noun of action from past participle stem of circumspicere "to look around" (see circumspect).
circumstance (n.): early 13c., "conditions surrounding and accompanying an event," from Old French circonstance "circumstance, situation," also literally, "outskirts" (13c., Modern French circonstance), from Latin circumstantia "surrounding condition," neuter plural of circumstans (genitive circumstantis), present participle of circumstare "stand around, surround, encompass, occupy, take possession of" from circum "around" (see circum-) + stare "to stand" from PIE root *stā- "to stand" (see stet). The Latin word is a loan-translation of Greek peristasis.

Meaning "a person's surroundings, environment" is from mid-14c. Meaning "a detail" is from c. 1300; sense of "that which is non-essential" is from 1590s. Obsolete sense of "formality about an important event" (late 14c.) lingers in Shakespeare's phrase pomp and circumstance ("Othello" III, iii).
circumstances (n.): "condition of life, material welfare" (usually with a qualifying adjective), 1704, from circumstance.
circumstantial (adj.): c. 1600, from Latin circumstantia (see circumstance) + -al (1). Related: Circumstantially. Circumstantial evidence is attested by 1691.
circumstantiate (v.): 1650s, from Latin circumstantia "surrounding condition" (see circumstance) + -ate (2). Related: Circumstantiated; circumstantiating; circumstantiation.
circumvent (v.): mid-15c., "to surround by hostile stratagem," from Latin circumventus, past participle of circumvenire "to get around, be around, encircle, surround," in figurative sense "to oppress, assail, cheat," from circum "around" (see circum-) + venire "to come" (see venue). Meaning "to go round" is from 1840. Related: Circumvented; circumventing.
circumvention (n.): early 15c., from Latin circumventionem (nominative circumventio), noun of action from past participle stem of circumvenire "to get around" (see circumvent).
circumvolution (n.): mid-15c., noun of action from past participle stem of Latin circumvolvere "to revolve through, to roll around" (see circumvolve).
circumvolve (v.): 1640s, from Latin circumvolvere "to roll round, revolve," from circum- (see circum-) + volvere "to turn around, roll" (see volvox). Related: Circumvolved; circumvolving.
circus (n.): late 14c., in reference to ancient Rome, from Latin circus "ring, circular line," which was applied by Romans to circular arenas for performances and contests and oval courses for racing (especially the Circus Maximus), from or cognate with Greek kirkos "a circle, a ring," from PIE *kirk- from root *(s)ker- (3) "to turn, bend" (see ring (n.)).

In reference to modern large arenas for performances from 1791; sense then extended to the performing company, hence "traveling show" (originally traveling circus, 1838). Extended in World War I to squadrons of military aircraft. Meaning "lively uproar, chaotic hubbub" is from 1869. Sense in Picadilly Circus and other place names is from early 18c. sense "buildings arranged in a ring," also "circular road." The adjective form is circensian.
cire (adj.): 1921, from French ciré, literally "waxed" (12c.), from Latin cera "wax" (see cere (n.)). Often short for ciré silk.
cirque (n.): c. 1600, "a circus," from French cirque (14c.), from Latin circus (see circus). Compare Italian and Spanish circo.
cirrhosis (n.): 1827, coined in Modern Latin by French physician René-Théophile-Hyacinthe Laennec (1781-1826) with -osis and Greek kirrhos "tawny," which is of unknown origin. So called for the orange-yellow appearance of the diseased liver. Related: Cirrhotic.
cirro-: word-forming element meaning "involving cirrus clouds," from comb. form of Latin cirrus (see cirrus).
cirrocumulus (n.): 1803, from cirrus + cumulus.
cirrous (adj.): 1650s in biology; 1815 in meteorology, from Latin cirrus (see cirrus) + -ous.
cirrus (n.): 1708, "curl-like fringe or tuft," from Latin cirrus "a lock of hair, tendril, curl, ringlet of hair; the fringe of a garment." In meteorology, cirrus clouds attested from 1803. So called from fancied resemblance of shape.
cis-: word-forming element meaning "on the near side of, on this side," from Latin preposition cis "on this side" (in reference to place or time), related to citra (adv.) "on this side," from PIE *ki-s, from root *ko- "this" (source also of Old Church Slavonic si, Lithuanian šis, Hittite ki "this," Old English hider, Gothic hidre "hither;" see he). Opposed to trans- or ultra-. Originally only of place, sometimes 19c. of time; 21c. of life situations (such as cis-gender, by 2011).
cisalpine (adj.): 1540s, from Latin cisalpinus "on this side of the Alps" (from the Roman point of view), from cis- (see cis-) + Alpinus "Alpine" (see Alpine). Compare ultramontane.
ciseaux (n.): 1892 in dance, French (plural), literally "scissors" (see scissors).
cismontane (adj.): from Latin cis- "on this side of" (see cis-) + stem of mons (see mount (n.1)).
cissy (n.): chiefly British English variant of sissy (q.v.).
cist (n.): "sepulchral chest or chamber," 1804, in some cases from Latin cista "wickerwork basket, box," from Greek kiste "box, chest" (see chest); according to OED, in some cases from Welsh cist in cist faen "stone coffin," the first element of which is from the Latin word.
Cistercian (adj.): c. 1600, "pertaining to the Cistercian order of monks," with -an + Medieval Latin Cistercium (French Cîteaux), site of an abbey near Dijon, where the monastic order was founded 1098 by Robert of Molesme. As a noun, "monk of the Cistercian order," from 1610s.
cistern (n.): mid-13c., from Old French cisterne "cistern; dungeon, underground prison" (12c., Modern French citerne), from Latin cisterna "underground reservoir for water," from cista "chest, box," from Greek kiste "box, chest" (see chest).
cit (n.): colloquial shortening of citizen, 1640s; contrasted to a countryman or a gentleman, usually with some measure of opprobrium (Johnson defines it as "A pert low townsman; a pragmatical trader").