1818, as a term in church administration, from plural + -ism. Attested from 1882 as a term in philosophy for a theory which recognizes more than one ultimate principle. In political science, attested from 1919 (in Harold J. Laski) in sense "theory which opposes monolithic state power." General sense of "toleration of diversity within a society or state" is from 1933. Related: Pluralist (1620s, in the church sense); pluralistic.
