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.
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.
"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.