The granular stuff you find in your pocket

I’ve been trying to find this for years. My late mother lived in Marrakesh and Fez for a few years, and she always referred to certain kinds of small, unidentifiable stuff (like pocket lint, or the gunk in the corner of your eye) as “fnaask”. She always said this was slang from Maroc, but I’ve been searching for a week now and can’t find any mention of such a word anywhere. So help me here: was she nuts, or is my memory failing?