invertebrate vs subnormal

invertebrate

noun
  • A spineless person; a coward. 

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

adj
  • Cowardly, uncourageous; lacking character. 

  • Lacking a backbone; without vertebrae. 

subnormal

noun
  • A person whose abilities are less than normal. 

  • That part of the axis of a curved line which is intercepted between the ordinate and the normal. 

adj
  • denormal 

  • Less than normal. 

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