(Greek > Latin: unable to speak, inarticulate, dumb; uttering no sound, silent, silence, still, quiet)

Cave tibi cane muto, aqua silente. (Latin expression)
Translation: "Beware of the silent dog and still water."

A Latin idiom: "Stagnant water can poison you." "Silent dogs can bite." Some Romans believed that taciturn (uncommunicative) adversaries were more dangerous than the ones who made a lot of noise.

mute (verb), mutes; muted; muting
1. To soften or muffle the sound of.
2. To reduce the tone, color, shade, or intensity of something.
mute (adjective), more mute, most mute
1. A reference to not producing speech or vocal sounds: A mute clip pad, or other device is used to soften, to deaden, or to muffle the sound of a musical instrument.
2. Pertaining to being unable to speak or to vocalize, as certain animals.
3. In linguistics, relating to that which is not pronounced; silent: An example of mute is the "e" in the word "house".
4. Descriptive of someone who is incapable of speech; not making any sounds; silent: A person may be mute because of deafness, loss of or damage to the tongue, etc.
muteness (s) (noun) (no plural)
Someone who is unable to speak because of deafness or damage to his or her larynx or vocal cords: Jacob is an example of muteness because he can't answer any questions his doctor asks him regarding his ailment.
mutism (s) (noun), mutisms (pl)
A refusal or inability to speak either at all times or on specific occasions, which may indicate trauma or stress: David is experiencing many mutisms even though he would like to converse with his wife and children.
selective mutism (SM) (s) (noun), selective mutisms (pl)
A seemingly incongruous behavior in which someone exhibits a ready flow of speech in private, but silence in public: Little Patrick can talk with members of his family; however, he never says anything when he is at school.

Silence words. More silence-content words at these links: silen- and tacit-.