σιωπάωsiōpáōStrong's G4623

properly, muteness, i.e. involuntary stillness, or inability to speak; and thus differing from G4602, which is rather a voluntary refusal or indisposition to speak, although the terms are often used synonymously); to be dumb (but not deaf also, like 2974 properly); figuratively, to be calm (as quiet water)

Derivation: from σιωπή (silence, i.e. a hush