mucus (n.) Look up mucus at Dictionary.com
1660s (replacing Middle English mucilage), from Latin mucus "slime, mold, mucus of the nose, snot," from PIE root *meug- "slippery, slimy," with derivatives referring to wet or slimy substances or conditions (cognates: Latin emungere "to sneeze out, blow one's nose," mucere "be moldy or musty," Greek myssesthai "to blow the nose," myxa "mucus," mykes "fungus," Sanskrit muncati "he releases"). Old English had horh, which may be imitative.