possumhaw vs white alder

possumhaw

noun

  • American winterberry, Ilex verticillata. 

  • Deciduous Holly, Ilex decidua. 

white alder

noun

  • American winterberry (Ilex verticillata). 

  • Grey alder (Alnus incana) 

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