inflexibleness vs motivation

inflexibleness

noun
  • Obstinacy of will or temper; firmness of purpose that will not yield to importunity or persuasion; unbending pertinacity. 

  • The quality or state of being inflexible 

motivation

noun
  • Willingness of action especially in behavior. 

  • Something which motivates. 

  • A research rating that measures how the rational and emotional elements of a commercial affect consumer intention to consider, visit, or buy something. 

  • The action of motivating. 

  • An incentive or reason for doing something. 

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