Meaning

noun the precipitate produced by sewage treatment

noun any thick, viscous matter

originFrom Middle English slugge, sluche (“mud, mire”), probably an alteration of Middle English sliche, slicche ("mud, slush, tar"; whence Modern English slitch), from Old English *sliċ, from Proto-West Germanic *sliki, *slīk, from Proto-Germanic *slikiz, *slīką (“mud, slush”). Cognate with Dutch slijk, German Schlick. Compare also slush.

Etymology from Wiktionary, CC BY-SA 3.0