lady's bower vs maiden's honesty

lady's bower

noun
  • Clematis vitalba, a climbing clematis with fragrant blossoms. 

maiden's honesty

noun
  • A plant of the species Clematis vitalba, evergreen clematis, a vine, native to the chalk and limestone soils of Britain, often considered invasive and noxious elsewhere. 

How often have the words lady's bower and maiden's honesty occurred in a corpus of books? (source: Google Ngram Viewer )