Can i get a list of all unique indexed words?

I have a requirement to provide a book-style browseable ‘index’ of all
our resources (which are already indexed with ferret). I thought that a
nice simple way to do this would be to pull every unique indexed word
from the ferret index, so that when the user clicks on a word in the
index, i just do a regular ferret search using that word.

With this approach, the only work i need to do is to generate the list
of terms in the first place (and refresh it occasionally). Is there a
way to pull this out of the ferret index somehow? It doesn’t have to
happen in real time, i could do it in a cron job and save the results to
a text file, or whatever. So, i don’t mind if it’s a slow process.

Grateful for any advice - max