It's not often that I come across a word that I have not heard. It is even less often that when I do see a new word that I can't at least roughly discern the meaning of it's root.
Someone today wanted to know what the word 'affiant' meant. I didn't hear it in the context of a sentence so I couldn't even begin to define it. In fact, the spell checker built in to Firefox didn't even know what the word was.
From Dictionary.com here is the word 'Affiant'