hickwall vs yaffle

hickwall

noun
  • A European green woodpecker, Picus viridis. 

  • A lesser spotted woodpecker, Dryobates minor. 

yaffle

noun
  • The European green woodpecker, Picus viridis. 

verb
  • Of the green woodpecker: to make its distinctive cry. 

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