inept vs subnormal

inept

adj
  • Unfit; unsuitable. 

  • Not able to do something; not proficient; displaying incompetence. 

subnormal

adj
  • denormal 

  • Less than normal. 

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. 

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