hyperkinesis vs stiffness

hyperkinesis

noun
  • Abnormally increased and sometimes uncontrollable activity or muscular movements. 

  • A condition especially of childhood characterized by hyperactivity. 

stiffness

noun
  • muscular tension due to unaccustomed or excessive exercise or work; soreness. 

  • inelegance; a lack of relaxedness. 

  • rigidity or a measure of rigidity. 

  • inflexibility or a measure of inflexibility. 

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