invertebrate vs mollusc

invertebrate

noun
  • A spineless person; a coward. 

  • An animal without vertebrae, i.e. backbone. 

adj
  • Cowardly, uncourageous; lacking character. 

  • Lacking a backbone; without vertebrae. 

mollusc

noun
  • A weak-willed person. 

  • A soft-bodied invertebrate of the phylum Mollusca, typically with a hard shell of one or more pieces. 

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