possumhaw vs skokeberry

possumhaw

noun
  • American winterberry, Ilex verticillata. 

  • Deciduous Holly, Ilex decidua. 

skokeberry

noun
  • A pokeberry; a pokeweed (the plant Phytolacca americana or its dark red or purple fruit). 

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