invertebrate vs retromingent

invertebrate

adj
  • Cowardly, uncourageous; lacking character. 

  • Lacking a backbone; without vertebrae. 

noun
  • A spineless person; a coward. 

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

retromingent

adj
  • Cowardly. 

  • That urinates backwards; also used of such urination. 

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