wear down vs wear thin

wear down

verb
  • Used other than figuratively or idiomatically: see wear, down. 

  • To cause (someone) physical or mental fatigue. 

  • To eventually persuade or defeat (someone) through persistent effort. 

wear thin

verb
  • To lessen or weaken over time, as from overuse. 

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