Etymology
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dissident (adj.)

1530s, "different, at variance, disagreeing," from Latin dissidentem (nominative dissidens), present participle of dissidere "to be remote; disagree, be removed from," literally "to sit apart," from dis- "apart" (see dis-) + sedere "to sit," from PIE root *sed- (1) "to sit."

Meaning "dissenting, not conforming" is from 1837, originally in reference to an established church. Meaning "disagreeing in political matters" is by 1943.

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dissident (n.)

"one who differs or dissents from others," 1766, in reference to Protestants and other non-Catholics in Poland, from dissident (adj.). General sense of "an opponent or non-conformist with regard to a prevailing opinion, method, etc." is by 1790, at first especially with reference to religion. In the political sense it is used by 1940, coinciding with the rise of 20c. totalitarian systems, especially with reference to the Soviet Union.

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*sed- (1)

Proto-Indo-European root meaning "to sit."

It forms all or part of: assess; assiduous; assiento; assize; banshee; beset; cathedra; cathedral; chair; cosset; dissident; dodecahedron; Eisteddfod; ephedra; ephedrine; ersatz; icosahedron; inset; insidious; nest; niche; nick (n.) "notch, groove, slit;" nidicolous; nidification; nidus; obsess; octahedron; piezo-; piezoelectric; polyhedron; possess; preside; reside; saddle; sanhedrim; seance; seat; sedan; sedate; (adj.) "calm, quiet;" sedative; sedentary; sederunt; sediment; see (n.) "throne of a bishop, archbishop, or pope;" sessile; session; set (v.); sett; settle (n.); settle (v.); siege; sit; sitz-bath; sitzkrieg; size; soil (n.1) "earth, dirt;" Somerset; soot; subside; subsidy; supersede; surcease; tanist; tetrahedron; Upanishad.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit a-sadat "sat down," sidati "sits," nidah "resting place, nest;" Old Persian hadis "abode;" Greek ezesthai "to sit," hedra "seat, chair, face of a geometric solid;" Latin sedere "to sit; occupy an official seat, preside; sit still, remain; be fixed or settled," nidus "nest;" Old Irish suide "seat, sitting," net "nest;" Welsh sedd "seat," eistedd "sitting," nyth "nest;" Old Church Slavonic sežda, sedeti "to sit," sedlo "saddle," gnezdo "nest;" Lithuanian sėdėti "to sit;" Russian sad "garden," Lithuanian sodinti "to plant;" Gothic sitan, Old English sittan "to sit."

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