pokeweed vs skokeberry

pokeweed

noun
  • A poisonous North American plant, Phytolacca americana, with reddish stems, broad leaves, clusters of white flowers, and dark purple berries. 

skokeberry

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

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