convolvulus vs morning glory

convolvulus

noun
  • Any of several plants, of the genus Convolvulus, found in temperate climates, having small trumpet-shaped flowers. 

  • A species of hawkmoth, Agrius convolvuli. 

morning glory

noun
  • Several members of the family Convolvulaceae; climbing plants with trumpet shaped flowers. 

  • An involuntary erection present upon waking. 

  • A rolling cloud in the shape of a cylinder. 

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