True black cumin is definitely not kalonji, (also known by the misnomer black cumin).. it's not Nigella sativum aka black onion seed. (it's not an onion or allium either!)
Real black cumin is hard to come by (Hindi shahi jeera) and has a variety of botanical names ranging from Cuminum nigrum, to Bunium bulbocastanum, to Carum bulbocastanum, depending on the method of classification. It is grown in the drier regions such as Afghanistan, Iran and Iraq and the Rajasthan plains of India. It is smaller and has a more subtle flavour than ordinary cumin.
Also called black caraway, kala jeera, and many more names.