1422, from L. cohortem, acc. of cohors "enclosure," meaning extended to "infantry company" in Roman army (a tenth part of a legion) through notion of "enclosed group, retinue," from com- "with" + root akin to hortus "garden," from PIE *ghr-ti-, from base *gher- "to grasp, enclose" (see yard (1)). Sense of "accomplice" is first recorded 1952, Amer.Eng.