circusyoudaoicibaDictYouDict[circus 词源字典]
circus: [16] Latin circus meant literally ‘ring, circle’, but it was applied metaphorically by the Romans to the circular arena in which performances and contests were held. That was the original signification of the word in English, applied in a strictly antiquarian sense to the ancient world, and it was not until the late 18th century that it began to be used for any circular arena and the entertainment staged therein.

The Latin word is related to, and may have come from, Greek kírkos; and it is also connected with Latin curvus, source of English curve. It has additionally been linked with Latin corōna ‘circlet’, from which English gets crown. And it is of course, via its accusative form circum, the starting point of a wide range of English words with the prefix circum-, from circumference to circumvent (in this category is circuit [14], which goes back to an original Latin compound verb circumīre, literally ‘go round’).
=> circle, circuit, circulate, crown, curve, search[circus etymology, circus origin, 英语词源]
circus (n.)youdaoicibaDictYouDict
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.