to mutter: to talk about someone in a low, half-hidden voice, usually in complaint, instead of saying it to that person openly.
The word imitates the sound it names. It is a low, rolling noise made at the back of the throat, the kind of half-swallowed talk people fall into when they are unhappy but not ready to say so out loud. Greek writers used it of the cooing of doves and of the buzz running through a crowd, and that is close to its force in the New Testament: speech pitched low, aimed at someone, and kept out of that person's hearing.
Almost every time it appears, the low talk is complaint, and the shape of the scene repeats:
- hired workers mutter against the landowner who paid them exactly what he promised
- religious leaders mutter against Jesus' followers for eating with tax collectors and sinners
- a crowd mutters at his claim to have come down from heaven
- his own disciples mutter at a teaching they find too hard to take
In each of those the grievance is real to the speakers, and in each the grievance goes sideways rather than face to face. The related noun (γογγυσμός) names the grumbling itself, and there is even a word for the person who makes a habit of it (γογγυστής).
Paul gives the word its heaviest use. When he tells the Corinthians not to grumble, he is pointing back to Israel in the desert, where this is the standard word in the Greek Old Testament for the people's complaining against God and against Moses, translating the Hebrew verb for that murmuring (לוּן). There it is no small fault: the generation that grumbled died in the wilderness. So a word that sounds like ordinary peevishness carries, in the biblical story, the memory of a people who talked their way out of the promised land.
One place breaks the pattern. In John 7:32 a crowd is muttering about Jesus, but what they are saying is hopeful: they are wondering aloud whether he might be the promised one. There the word keeps only its sound, a subdued undercurrent of talk moving through a crowd, with no complaint in it at all.