fennel flower vs nigella

fennel flower

nigella

noun
  • 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. 

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

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