[1630–40; co- + defendant]This word is first recorded in the period 1630–40. Other words that entered Englishat around the same time include: amphibian, brigade, integrate, platoon, seesawco- is a prefix meaning “with,” “together,” “in association,” sometimes with the derivedsense “auxiliary, subsidiary” (coenzyme; copilot), and, in mathematics and astronomy, with the sense “complement” (codeclination)