Vigna unguiculata vs black-eyed pea

Vigna unguiculata

black-eyed pea

noun
  • An African leguminous plant, of the species Vigna unguiculata, widely cultivated as food and forage, specifically Vigna unguiculata subsp. unguiculata. 

  • The edible seed of these plants. 

  • Any pale bean with a black spot. 

How often have the words Vigna unguiculata and black-eyed pea occurred in a corpus of books? (source: Google Ngram Viewer )