inertness vs somnolence

inertness

noun
  • Lack of activity or exertion; habitual indisposition to action or motion 

  • Absence of the power of self-motion; inertia. 

  • Quality of being unreactive with other chemical compounds or elements. 

somnolence

noun
  • A state of drowsiness or sleepiness. 

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