inflexible vs polytropic

inflexible

adj
  • Not willing to change, e.g. one's opinion or habits. 

  • Not flexible; not capable of bending or being bent. 

  • Not able to be changed or adapted to circumstances. 

polytropic

adj
  • of any change in the thermodynamic properties of a gas in which its specific heat remains constant 

  • many-valued 

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