Geek

Stephen asked if I wanted to go to the geek shop (meaning the nerd store, the comic shop) and it got me thinking.... geek usually means a socially impaired brainiac egg-head, these days. I knew that before that it meant side-show freak. But, before that it apparently meant a simpleton or dunce.

Just like nerd... from meaning stupid, to freaky, to smart.
The evolution of a word from one meaning to it's polar opposite.