pocan vs white alder

pocan

noun
  • The poke, Phytolacca americana (formerly Phytolacca decandra). 

white alder

noun
  • American winterberry (Ilex verticillata). 

  • Grey alder (Alnus incana) 

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