σῑγάω · sigaō — LSJ
keep silence, used by Hom. only in imper. σίγα, hush! be still! Il. 14.90, Od. 17.393; σιγᾶν h.Merc. 93, Hdt. 8.61, 110; but freq. in Pi., Trag., and Att., as Pi. N. 10.29, A. Pr. 200, etc.; σ. περί τινος E. Hipp. 312; πρὸς οὓς δεῖ Pl. Phdr. 276a; πρὸς τοῦτο, ἐν τούτῳ, X. Cyr. 5.5.20, An. 5.6.27.
metaph. of things, σιγῶν δʼ ὄλεθρος καὶ μέγα φωνοῦντʼ . . ἀμαθύνει A. Eu. 935 (anap.); σύριγγες οὐ σιγῶσιν Id. Supp. 181; σίγησε δʼ αἰθήρ E. Ba. 1084; σ. πόντος, σ. ἀῆται, ἁ δʼ ἐμὰ οὐ σ. ἀνία Theoc. 2.38:—in E. Fr. 781.13, τὰ σιγῶντʼ ὀνόματʼ . . δαιμόνων seems to be = τὰ ἄρρητα, secret, mystical:—Pass., μέμψομαι σιωπὴν ὡς ἐσιλγήθη κακῶς I shall impute as a fault that silence was kept, Id. Supp. 298; also τί σεσίγηται δόμος Ἀδμήτου; why is it all silent? Id. Alc. 78; σιγῶντα λέγειν, λέγοντα σιγᾶν
trans., hold silent, keep secret, Pi. Fr. 81, A. Pr. 106, 441, Ag. 36, Hdt. 7.104 (s. v. l.), etc.:—Pass., to be kept silent or secret, σεσιγαμένον χρῆμα Pi. O. 9.103; ὁ θάνατος . . ἐσιγήθη Hdt. 5.21; σιγώμενος S. Fr. 653; ἐσιγάθη δʼ ἂν ὑφορβός would never have been heard of, Theoc. 16.54.