If you have been watching Game of Thrones, then you would have heard the word "wight". In literature this word is used to refer to some kind of supernatural entity, whether it is a ghost or even a god. Sometimes it can also be used to refer to some kind of monster. In previous centuries the word "wight" was used to refer to a living creature, but was mostly used for people. Game of Thrones combined these two to to name the monstrous undead controlled by the White Walkers (not the Wight Walkers, yes, a bit confusing).
What does this have to do with "not"? Well, in an even older version of English called Old English, the word "wight" was "wiht" and it refered not just to people, and creatures, but to anything that you didn't have a specific name for, exactly how we use the word "thing" in Modern English.
"not" comes from a compound word in Old English "nāwiht" which was literally "not anything". This eventually became Middle English not, noght and naht. From here we got "not", "nought" and "nawt".
So a word meaning a thing has gone all the way from being very general, to a word that is obscure enough that you might not have even realised that the creatures in Game of Thrones are called "wights". At first I thought they were just called "whites" after the "White Walkers". It's really funny how some words change so much over time but others, like "not", hardly change at all