late 14c., "a circumference; a periphery, a line going around (an area), whether circular or not; a circular or circuitous course," from Old French circuit (14c.) "a circuit; a journey (around something)," from Latin circuitus "a going around," from stem of circuire, circumire "go around," from circum "round" (see circum-) + ire "to go" (from PIE root *ei- "to go").
From c. 1400 as "space enclosed within certain limits." Hence, "district in which any business involving periodic journeys is done (1570s), especially of judicial assignments involving the journey of a judge from one place to another; in reference to routes followed by itinerant entertainers from 1834. Hence also circuit-rider "Methodist minister who rides a circuit, preaching successively in different stations" (by 1834); to ride circuit "take a roundabout course" is from 1650s.
Electrical sense "arrangement by which a current is kept up between two poles" is from 1746. Circuit-breaker "device for automatically opening an electrical circuit" is recorded from 1874. Related: Circuital.