Etymology
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conscientious (adj.)

1610s, of persons, "controlled by conscience, governed by the known rules of right and wrong;" of conduct, etc., "regulated by conscience," 1630s, from French conscientieux (16c.; Modern French consciencieux), from Medieval Latin conscientiosus, from Latin conscientia "sense of right, moral sense" (see conscience). Related: Conscientiously; conscientiousness.

Conscientious objector is from 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] 

Slang shortening conchy is attested from 1917.

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challenger (n.)
late 13c., "a claimant;" mid-14c., "one who makes false charges;" mid-15c., "one who disputes something, objector," from Anglo-French chalengeour (Old French chalongeor "slanderer, petitioner, plaintiff"), agent noun from challenge (v.). Specific sense of "one who calls out another in a contest" is from 1510s.
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affirmation (n.)

early 15c., "assertion that something is true," from Old French afermacion "confirmation" (14c.), from Latin affirmationem (nominative affirmatio) "an affirmation, solid assurance," noun of action from past-participle stem of affirmare "to make steady; strengthen; confirm," from ad "to" (see ad-) + firmare "strengthen, make firm," from firmus "strong" (see firm (adj.)). In law, as the word for the conscientious objector alternative to oath-taking (Quakers, Moravians, etc.), it is attested from 1690s; if false, it incurs the same penalty as perjury.

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