low tide vs retrocession

low tide

noun
  • The tide at its lowest level for a particular tidal cycle at a certain place. 

  • The time of day when the sea has receded to its lowest level. 

retrocession

noun
  • The transfer of risk from one reinsurer to another. 

  • The act of retroceding; a going back. 

  • 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 low tide and retrocession occurred in a corpus of books? (source: Google Ngram Viewer )