late 14c., in reference to the large, oblong, unroofed enclosures used for races, etc., in 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," perhaps from PIE *kikro-, reduplicated form of root *sker- (2) "to turn, bend." The adjective form is circensian.
In reference to modern large arenas for performances of feats of horsemanship, acrobatics, etc., from 1791, sense then extended to the performing company itself and the entertainment given, 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."
"of or pertaining to the (Roman) circus," 1590s, from Latin circensis "of the circus," from circus (see circus).
"rounded, made circular," 1830, from Latin circinatus, past participle of circinare "to make round," from circus "ring" (see circus). Related: Circination.
1590s, "investigate or study (a matter) closely, search or examine with continued care," from French recercher, from Old French recercher "seek out, search closely," from re-, here perhaps an intensive prefix (see re-), + cercher "to seek for," from Latin circare "go about, wander, traverse," in Late Latin "to wander hither and thither," from circus "circle" (see circus).
The intransitive meaning "make researches" is by 1781. Sometimes 17c. also "to seek (a woman) in love or marriage." Related: Researched; researching.
"much sought-after, uncommon, rare," 1722, from French recherché "carefully sought out," past-participle adjective from rechercher "to seek out" (12c.), from re-, here perhaps suggesting repeated activity (see re-) + chercher "to search," from Latin circare, in Late Latin "to wander hither and thither," from circus "circle" (see circus). Commonly used 19c. of food, styles, etc., to denote obscure excellence. "Àla recherchedu temps perdu" is the title of Proust's great novel of reminiscence (1913).
c. 1300, serchen, "go through and examine carefully and in detail" (transitive), from Old French cerchier "to search" (12c., Modern French chercher), from Latin circare "go about, wander, traverse," in Late Latin "to wander hither and thither, go round, explore," from circus "circle" (see circus). Compare Spanish cognate cercar "encircle, surround."
The meaning "make an examination of" a person, bags, etc., is from early 15c. Phrase search me as a verbal shrug of ignorance is recorded by 1901. Search engine attested from 1988. The phrase search-and-destroy as a modifier is by 1966, American English, a coinage from the Vietnam War. Search-and-rescue is by 1944.
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.