hopniss
Apios americana, a perennial vine that bears edible beans and large edible tubers.
You have to cook hopniss tubers—they are inedible and potentially toxic raw. They are great boiled, roasted, or fried.
Where it comes from
Borrowed from Unami hopënis (/hopənis/ (which has now shifted to meaning "potato"), compare Munsee óhpən, ohpën (“potato”)), possibly via Colonial Swedish. Compare katniss.
Adapted from the Wiktionary entry hopniss (CC BY-SA 4.0).