overburden vs wear down

overburden

verb
  • To overload or overtax. 

noun
  • A sterile stratum that lies above the stratum being investigated 

  • The rock and subsoil that lies above a mineral deposit such as a coal seam. 

wear down

verb
  • To cause (someone) physical or mental fatigue. 

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

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

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