late 14c., "a going around; a line going around," 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" (see ion). Electrical sense is from 1746. Of judicial assignments, from 1570s; of venues for itinerant entertainers, from 1834. Circuit breaker is recorded from 1874. Related: Circuital.