low tide vs weakening

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. 

weakening

noun
  • A structural principle of mathematical logic that states that the hypotheses of any derived fact may be freely extended with additional assumptions. 

  • An instance or process of loss of strength. 

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