cowpea vs crowder pea

cowpea

noun
  • Any of the plants in the species Vigna unguiculata, including the black-eyed pea. 

crowder pea

noun
  • A type of cowpea, Vigna unguiculata, closely related to the black-eyed pea, but without the characteristic black spot. 

  • The black-eyed pea. 

How often have the words cowpea and crowder pea occurred in a corpus of books? (source: Google Ngram Viewer )