calla lily vs lily of the Nile

calla lily

noun
  • A common name for certain flowering plants in the genus Zantedeschia; not related to either the genus Calla or the true lilies (Liliaceae) 

  • A flower of one of these plants. 

lily of the Nile

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

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

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