black cumin vs nigella

black cumin

noun
  • A spice plant with aromatic seeds (Nigella sativa). 

  • A cultivated variety of cumin (Cuminum cyminum). 

  • A spice plant related to cumin with dark seeds and an edible root (Bunium bulbocastanum). 

nigella

noun
  • The seeds of the plant Nigella sativa, used as a culinary spice. 

  • Any plant of the genus Nigella of about twelve species of annual flowering plants, the blooms of which are generally blue in colour but also found in shades of pink, white and pale purple. 

How often have the words black cumin and nigella occurred in a corpus of books? (source: Google Ngram Viewer )