adverb
never; by no means; not in the least
Emphatic negative adverb used with a negative verb. Stronger than 少しも or 決して. Literary and somewhat old-fashioned.
彼の言葉をつゆいささかも疑わなかった。
I never doubted his words in the slightest.
その知らせを聞いても、つゆいささかも驚かなかった。
Even hearing that news, I was not surprised in the least.