οὐκ ἔστι σιγᾶν αἰσχρόν, ἀλλ' εἰκῆ λαλεῖν → keeping silence is not shameful; speaking at random is (Menander)
per-nĕcesse:I adj. indecl., very necessary, indispensably necessary: cum pernecesse esset, Cic. Tull. 21, 49.