pernecesse
From LSJ
Ἐμπειρία γὰρ τῆς ἀπειρίας κρατεῖ → Inscitiam etenim vincit experientia → Erfahrung überwindet Unerfahrenheit
Latin > English (Lewis & Short)
per-nĕcesse:
I adj. indecl., very necessary, indispensably necessary: cum pernecesse esset, Cic. Tull. 21, 49.