Words easily shift between meaning ‘anything’ ‘something’ and ‘nothing’. If I ask “Did you see something?” or “Did you see anything?” or “Didn’t you see anything?” they all mean pretty much the same thing – even the negative question will find out whether or not you saw anything.
If you didn’t, you could answer:
No, I didn’t see anything.
OR
No, I saw nothing.
But in Italian, and Spanish, Old English, and colloquial modern English, you could also say:
No, I didn’t see nothing.
So dim used to mean ‘anything’ (and still does, in certain phrases); but from being used in negative sentences like “I didn’t see anything”, it kind of shifts to usually mean ‘nothing’. ‘Rien’ in French has done the same – more here and in the replies to it.