impaired vs subnormal

impaired

adj
  • Rendered less effective. 

  • inebriated, drunk. 

noun
  • A criminal charge for driving a vehicle while impaired. 

subnormal

adj
  • Less than normal. 

  • denormal 

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 impaired and subnormal occurred in a corpus of books? (source: Google Ngram Viewer )