(not) the slightest bit; (not) at all
Formal/literary negative-polarity item used with a negative predicate, often as 寸毫も〜ない. Emphasizes that something is not present even in the smallest amount.
There is not the slightest bit of truth in his story.
There was no room for doubt at all.
Compound of 寸 (すん, a small unit of length) and 毫 (ごう, fine hair or minute amount), literally 'even a tiny bit'. The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning of a minuscule quantity.