Etymology
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soil (v.)
early 13c., "to defile or pollute with sin," from Old French soillier "to splatter with mud, to foul or make dirty," originally "to wallow" (12c., Modern French souillier), from souil "tub, wild boar's wallow, pigsty," which is from either Latin solium "tub for bathing; seat" (from PIE *sodio- "seat," from root *sed- "to sit") or Latin suculus "little pig," from sus "pig." Literal meaning "to make dirty, begrime" is attested from c. 1300 in English. Related: Soiled; soiling.
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soil (n.1)
c. 1300, originally "land, area, place," from Anglo-French soil "piece of ground, place" (13c.), from a merger or confusion of Old French sol "bottom, ground, soil" (12c., from Latin solum "soil, ground;" see sole (n.1)), Old French soeul, sueil "threshold, area, place" (from Latin solium "seat," from PIE *sodio- "seat," from PIE root *sed- (1) "to sit"), and Old French soil, soille "a miry place," from soillier (see soil (v.)).

Meaning "place of one's nativity" is from c. 1400. Meaning "mould, earth, dirt" (especially that which plants grow in) is attested from mid-15c.
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soil (n.2)
"filth, dirt, refuse matter, sewage, liquid likely to contain excrement," c. 1600, earlier "miry or muddy place" (early 15c.), from Old French soille "miry place," from soillier (v.) "to make dirty," and in part a native formation from soil (v.). This is the sense in archaic night-soil.
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free-soil (adj.)
in U.S. history, "opposed to expansion of slavery into the territories," 1846, from free soil (n.) in reference to settled regions without slavery, from free (adj.) + soil (n.). Related: Free-soiler.
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topsoil (n.)
also top-soil, 1789, from top (adj.) + soil (n.).
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sully (v.)

1590s, probably from French souiller "to soil," also figurative, from Old French soillier "make dirty" (see soil (v.)). Related: Sullied (1570s); sullying.

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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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solum (n.)
Latin, "ground, soil," of unknown origin.
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autochthonic (adj.)
"native, sprung from the soil," 1827, from autochthon + -ic.
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