expression, noun
feigning complete ignorance; claiming to know nothing
Set phrase used when someone pretends to have no knowledge of a matter, often to avoid responsibility or involvement. The repetition of 'know not' in two synonymous verbs (知る and 存ずる) emphasizes total denial.
彼はその件について知らぬ存ぜぬを決め込んだ。
He feigned complete ignorance about the matter.
問い詰められても、知らぬ存ぜぬで通そうとした。
Even when pressed, he tried to get by with claiming to know nothing.
A set phrase combining the classical negative forms of 知る (to know) and 存ずる (to know, humble). The repetition reinforces the idea of complete ignorance. The exact origin is uncertain, but it likely emerged as an emphatic legal or formal denial.