Venus' comb vs shepherd's needle

Venus' comb

noun

  • An umbelliferous plant, Scandix pecten-veneris. 

shepherd's needle

noun

  • Beggarticks (Bidens spp.) 

  • Venus' comb (Scandix pecten-veneris) 

How often have the words Venus' comb and shepherd's needle occurred in a corpus of books? (source: Google Ngram Viewer )