cultivar vs phylum

cultivar

noun
  • A cultivated (not necessarily botanical) variety of a plant species or hybrid of two species. 

phylum

noun
  • A rank in the classification of organisms, below kingdom and above class; also called a divisio or a division, especially in describing plants; a taxon at that rank 

  • A large division of possibly related languages, or a major language family which is not subordinate to another. 

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