tail off vs wane

tail off

verb
  • To gradually subside or diminish; to tail away. 

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. 

  • ]] 

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