American winterberry vs winterberry

American winterberry

noun
  • Ilex verticillata, a species of holly native to eastern North America in the United States and southeast Canada, from Newfoundland west to Ontario and Minnesota, and south to Alabama. 

winterberry

noun
  • A species of holly native to the United States and Canada and producing red berries, Ilex verticillata. 

  • The fruit of this plant. 

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