c. 1400, "to desecrate, profane;" mid-15c., "to make foul or dirty," also "to rape, deflower," alteration of earlier defoulen, from Old French defouler "trample down, violate," also "ill-treat, dishonor," from de- "down" (see de-) + foler "to tread," from Latin fullo "person who cleans and thickens cloth by stamping on it" (see foil (v.1)).

The alteration (or re-formation) in English is from influence of Middle English filen (v.) "to render foul; make unclean or impure," literal and figurative, from Old English fylen (trans.), related to Old English fulian (intrans.) "to become foul, rot," from the source of foul (adj.). Compare befoul, which also had a parallel form befilen. Related: Defiled; defiling.

"narrow passage in a mountain region," 1640s, especially in a military sense, "a narrow passage down which troops can march only in single file," from French défilé, noun use of past participle of défiler "march by files" (17c.), from de- "off" (see de-) + file "row," from Latin filum "thread" (from PIE root *gwhi- "thread, tendon"). The verb, "to march off in a line or file," is by 1705, from French défiler.

1570s, "that which defiles," from defile (v.) + -ment. From 1630s as "act of making foul; state of being unclean."

"arrangement in fortification to protect the lines from enfilading fire," 1828, from defile (n.) + -ade. Related: Defilading.

c. 1300, undefylde, from un- (1) "not" + past participle of defile (v.). Originally of morals; sexual sense is attested from mid-15c. Physical sense of "not made dirty" is from 1580s.

*gwhī-, Proto-Indo-European root meaning "thread, tendon."

It forms all or part of: defile (n.) "narrow passage;" enfilade; filament; file (v.1) "place (papers) in consecutive order for future reference;" filigree; filipendulous; fillet; profile.

It is the hypothetical source of/evidence for its existence is provided by: Avestan jya- "bowstring;" Latin filum "a thread, string;" Armenian jil "sinew, string, line;" Lithuanian gysla "vein, sinew;" Old Church Slavonic zila "vein."

late 14c., polluten, "to defile, violate the sanctity of, render ceremonially unclean," a back formation from pollution, or else from Latin pollutus, past participle of polluere "to defile, pollute, contaminate." Related: Polluted; polluting. Meaning "make physically foul" is from 1540s; specific sense "contaminate the environment" emerged by 1860, but was not yet in the 1895 Century Dictionary.

"to defile; make filthy," 1590s, from dirty (adj.). Related: Dirtied; dirtying.

spot on skin, Old English mal "spot, mark, blemish," especially on cloth or linen, from Proto-Germanic *mailan "spot, mark" (source also of Old High German meil, German Mal, Gothic mail "wrinkle"), from PIE root *mai- (2) "to stain, soil, defile" (source also of Greek miainein "to stain, defile," see miasma). Specifically of small, permanent dark marks on human skin from late 14c.

early 15c., "infect with a disease, defile," from Latin contaminatus, past participle of contaminare "to defile, to corrupt, to deteriorate by mingling," originally "to bring into contact," from contamen "contact; pollution," from assimilated form of com "with, together" (see con-) + *tag-, base of tangere "to touch" (from PIE root *tag- "to touch, handle"). Related: Contaminant (1934).