demobilize vs perturb

demobilize

verb
  • To disband troops, or remove them from a war footing. 

  • To release someone from military duty, especially after a war. 

perturb

verb
  • To disturb; to bother or unsettle. 

  • To modify the motion of a body by exerting a gravitational force. 

  • To modify slightly, such as an equation or value. 

  • To slightly modify the motion of an object. 

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