the.com/whit

The smallest unit of caring, almost always used when you have none.

means A tiny particle or least possible amount of something—used almost exclusively in negatives, like 'not a whit.'

from Whit traces back to Old English 'wiht,' meaning a creature, thing, or being—the same root that gives us 'naught' (literally 'no wiht,' no thing). Over time 'wiht' shrank from meaning any entity at all down to the smallest conceivable speck of one, which is why it now shows up almost only when something measures zero of it.

origin
From Old English wiht, meaning creature or thing
usage
Survives mainly in the phrase not a whit
size
Smaller than a jot, bigger than nothing
relative
Cousin to whittle, not to white
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