How Well Do You Know English Slang?
1896, in reference to those with religious scruples about mandatory vaccination. Military sense predominated from World War I.
After a chequered career full of startling episodes and reversals, the Vaccination Bill becomes virtually the Vaccination Act. In Parliament the hottest of the contest centred round the conscientious objector. [The Lancet, Aug. 13, 1898]
A person who refuses to render military service on the grounds of moral principle or religious belief. A CO must demonstrate a sincere, active, and long-standing objection in order to receive an exemption from armed service. The United States and some European governments officially recognize CO status; approved COs are usually required to perform social service or noncombat military service in place of armed duty. (See also draft, draft dodger, and Selective Service System.)