ἀπερινοήτως
From LSJ
Ἐς δὲ τὰ ἔσχατα νουσήματα αἱ ἔσχαται θεραπεῖαι ἐς ἀκριβείην, κράτισται → For extreme diseases, extreme methods of cure, as to restriction, are most suitable.
Russian (Dvoretsky)
ἀπερινοήτως: незаметно, врасплох (παρεισπίπτειν Polyb.).
Spanish
incomprensiblemente, irreflexivamente, poco inteligentemente