Do fwata an is "because I can."
This is a bit of grammar I've used before, but never put into the grammar document explicitly. An is just there to complete all the required parts of the verb, since "can" and "do" are both contained in fwata.
I was giving some thought to another blog (as if I kept up with the ones I already have) of translations and compositions in Nevashi, and maybe with guest appearances of ea-luna, Myjador (or however I was spelling that last), and that unnamed conlang I've been secretly working on. I thought I'd call it either "Do Fwata An" or "Mufmuf".
If you've ever needed to say that someone writes too much, mufmuf is your verb, modeled on tel/teltel. Si mufmuf. ("S/he writes too much.") And isn't that fun to say?