Etymology of English Language

Circle:
meaning:
A plane curve everywhere equidistant from a given fixed point, the center.
A group of people sharing an interest, activity, or achievement: well-known in artistic circles.
etymology:
c.1305, from O.Fr. cercle, from L. circulus "small ring," dim. of circus (q.v.). Replaced O.E. trendel and hring. Meaning "group of persons surrounding a center of interest" is from 1714; that of "coterie" is from 1646; dim. form circlet is from 1481. The verb is from c.1374 .

Circus:
meaning:
A public entertainment consisting typically of a variety of performances by acrobats, clowns, and trained animals.
A roofless oval enclosure surrounded by tiers of seats that was used in antiquity for public spectacles.

word history:
The modern circus owes its name, but fortunately not its regular program of events, to the amusements of ancient times. The Latin word circus, which comes from the Greek word kirkos, "circle, ring," referred to a circular or oval area enclosed by rows of seats for spectators. In the center ring, so to speak, was held a variety of events, including chariot races and gladiatorial combats, spectacles in which bloodshed and brutality were not uncommon. The first use of circus recorded in English, in a work by Chaucer written around 1380, probably refers to the Circus Maximus in Rome. Our modern circus, which dates to the end of the 18th century, was originally an equestrian spectacle as well, but the trick riders were soon joined in the ring by such performers as ropedancers, acrobats, and jugglers. Even though the circular shape of the arena and the equestrian nature of some of the performances are carried over from its Roman namesake, the modern circus has little connection with its brutal namesake of long ago.

etymology:
c.1380, from L. circus "ring," applied by Romans to circular arenas for performances and contests (esp. the Circus Maximus), from or akin to Gk. kirkos "a circle," from PIE *kirk- from base *(s)ker- "to turn, bend." First attested use for "traveling show" is 1791.

src: http://dictionary.reference.com/