pigeonweed vs skokeberry

pigeonweed

noun
  • Synonym of pokeweed (“the plant Phytolacca americana”) 

skokeberry

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

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