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.
1845, from back slum "dirty back alley of a city, street of poor or low people" (1825), originally a slang or cant word meaning "room," especially "back room" (1812), of unknown origin. Related: slums. Slumscape is from 1947.
"to cheat, to drive a hard bargain," 1824, from Jew (n.) (compare gyp, welsh, etc.). "Though now commonly employed without direct reference to the Jews as a race, it is regarded by them as offensive and opprobrious" [Century Dictionary, 1902]. The campaign to eliminate it in early 20c. was so successful that people also began to avoid the noun and adjective, using Hebrew instead.
Now I'll say 'a Jew' and just the word Jew sounds like a dirty word and people don't know whether to laugh or not. [Lenny Bruce, "How to Talk Dirty and Influence People," 1965]
"spittle, the secretions of the salivary glands of the mouth," early 15c. (Chauliac), salive, from Old French salive and directly from Latin saliva "spittle" (from Proto-Italic *sal-iwo- "dirty yellow," from PIE root *sal- (2) "dirty; gray; "see sallow (adj.)). Related: Salival.
word-forming element meaning "black," from Greek melano-, combining form of melas (genitive melanos) "black, dark, murky,"probably from a PIE root *melh-"black, of darkish color" (source also of Sanskrit malinah "dirty, stained, black," Lithuanian mėlynas"blue," Latin mulleus "reddish").