This term is not used much. Most know more about "random testing" or "monkey testing", much more common out there. I think fuzzing is used a lot to find security holes and I think it is kind of old, very used yet though, but it is not something that is seen everywhere by programmers outside of systems programming. Not all programmers work in the same field, so it is not uncommon for someone not to know about this. In my case, I associate the term fuzzing with matching, for example.