African lily vs lily of the Nile

African lily

noun
  • Any of certain flowering plants of the genus Agapanthus, especially Agapanthus umbellatus. 

lily of the Nile

noun
  • Agapanthus praecox, a plant species in the family Alliaceae. 

  • Zantedeschia aethiopica, a plant species in the family Araceae. 

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