black woodpecker vs hickwall

black woodpecker

noun
  • A bird of the species Dryocopus martius in the family Picidae. 

hickwall

noun
  • A European green woodpecker, Picus viridis. 

  • A lesser spotted woodpecker, Dryobates minor. 

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