combining form from Greek mýxa "nasal discharge, slime, nostril, snout, lamp wick," derivative from a base *muk- also in Greek mýssomai, mýssesthai "to blow one's nose, snort," apomýssein "to wipe (the nose)," myktḗr "nostril," perhaps going back to Indo-European *(s)muk- "nasal discharge," *(s)meuk- "undo, loosen, wipe off," whence Sanskrit múcyate "comes free, is freed," Old Church Slavic promŭknǫti sę "to spread, become known," Serbian & Croatian màknuti "to move," Polish zamknąć "to shut, close," and (with nasal present) Sanskrit muñcati "looses, frees," Lithuanian munkù, mùkti "to come free, get away," Latin ēmungere "to wipe one's nose" (with unexpected g)
The customary assumption is that the derivatives referring to nasal discharge in Greek and Latin are a specialization of the more general verbal meaning "loosen, wipe off" seen elsewhere. Greek mýxa has been compared directly with Latin mūcor "mucous substance, mustiness, mold" (with the two forms supposedly parallel to Greek knîsa, knī́sē "savor of burnt sacrifice, caul fat," Latin nīdor "strong smell, fumes"). However, the primary meaning of Latin mūc- (also in mūcus "nasal discharge," mūcēre "to be moldy," mūcidus "sniveling, moldy, musty") may be "dampness, mold." In this case the base might be comparable with Old Icelandic mugga "mugginess, drizzling mist," Danish mugg "mold," Old Danish mugen, muen "damp," Swedish mögel "mold" (cf. muggy), Latvian mukls "marshy." Whether the Greek forms should be linked to one or the other or represent a sort of merger of independent bases is unclear. All these words may have a partially phonesthemic character, reflected in the Greek variants with initial s (smýssetai, smyktḗr, recorded by Hesychius); these have been compared with Irish smug, smuga "mucus, snot," Scottish Gaelic smugaid "spittle" (but the sole earlier Irish form, Middle Irish smucli "mucus," may point to a different, perhaps purely phonesthemic origin for these).