I have no idea how the word is correctly spelled. The pronunciation is oo-nah-bul, with the emphasis on "oo". A friend who is a German teacher isn't familiar with the term. My grandmother was born in southeastern Kansas in the late 1880s. Any ideas out there?
It could be a poor pronunciation of "unable".
The german word " untauglich" means (among other things) unmannerly and incapable.
It is an archaic German word meaning awkward or unwieldy. If you Google "oonable awkward" there are a few sites that mention it.
Thanks to you both!