degeneration vs retrocession

degeneration

noun
  • A thing that has degenerated. 

  • The process or state of growing worse, or the state of having become worse. 

  • That condition of a tissue or an organ in which its vitality has become either diminished or perverted; a substitution of a lower for a higher form of structure. 

  • Gradual deterioration, from natural causes, of any class of animals or plants or any particular organ or organs; hereditary degradation of type. 

retrocession

noun
  • The act of retroceding; a going back. 

  • The transfer of risk from one reinsurer to another. 

  • The return of land, rights, etc. previously ceded. 

  • Metastasis of an eruption or tumour from the surface to the interior of the body. 

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