late 12c., fulthe, "corrupt, sinful," from filth + -y (2). Meaning "physically unclean, dirty, noisome" is from late 14c. Meaning "morally dirty, obscene" is from 1530s.
In early use often hardly more emphatic than the mod. dirty; it is now a violent expression of disgust, seldom employed in polite colloquial speech. [OED]
Related: Filthily; filthiness.
1590s, from French squalide and directly from Latin squalidus "rough, coated with dirt, filthy," related to squales "filth," squalus "filthy," squalare "be covered with a rough, stiff layer, be coated with dirt, be filthy," of uncertain origin. Related: Squalidly; squalidness; squalidity.
"to defile; make filthy," 1590s, from dirty (adj.). Related: Dirtied; dirtying.
late 14c., "dung, excrement, feces; filth, dirt," from Old French ordure "filth, uncleanliness" (12c.), from ord, ort "filthy, dirty, foul," from Latin horridus "dreadful" (see horrid). Related: Ordurous.