impetus vs recession

impetus

noun
  • The force or energy associated with a moving body; a stimulus. 

  • Anything that impels; a stimulating factor. 

  • An activity in response to a stimulus. 

  • A force, either internal or external, that impels; an impulse. 

  • A principle of motive force, held as exquivalent to weight times velocity by John Buridan, in an auxiliary theory of Aristotelian dynamics introduced by John Philoponus, describing projectile motion against gravity as linear until it transitions to a vertical drop and the intellectual precursor to the concepts of inertia, momentum and acceleration in classical mechanics. 

recession

noun
  • A procedure in which an extraocular muscle is detached from the globe of the eye and reattached posteriorly. 

  • The act or an instance of receding or withdrawing. 

  • A period of low temperatures that causes a reduction in species; ice age. 

  • A period of reduced economic activity 

  • The ceremonial filing out of clergy and/or choir at the end of a church service. 

  • The act of ceding something back. 

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