fall off vs wane

fall off

verb
  • To diminish in size, value, etc. 

  • To fall into sin; stray. 

  • To change the direction of the sail so as to point in a direction that is more down wind; to bring the bow leeward. 

  • To become detached or to drop from. 

wane

verb
  • To progressively lose its splendor, value, ardor, power, intensity etc.; to decline. 

  • Said of light that dims or diminishes in strength. 

  • Said of a time period that comes to an end. 

  • Said of the Moon as it passes through the phases of its monthly cycle where its surface is less and less visible. 

noun
  • A gradual diminution in power, value, intensity etc. 

  • The end of a period. 

  • The lunar phase during which the sun seems to illuminate less of the moon as its sunlit area becomes progressively smaller as visible from Earth. 

  • A child. 

  • A rounded corner caused by lack of wood, often showing bark. 

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