1610s, "hindered by loss, injury, or prejudice," past-participle adjective from disadvantage (v.). Of races or classes deprived of opportunities for advancement, from 1902, a word popularized by sociologists. As a noun, shorthand for disadvantaged persons, it is attested by 1939.
disabuse
disaccord
disaccordance
disaccustom
disadvantage
disadvantaged
disadvantageous
disaffect
disaffected
disaffection
disaggregate