retain vs topple

retain

verb
  • To hold back (a pupil) instead of allowing them to advance to the next class or year. 

  • To employ by paying a retainer. 

  • To keep in one's pay or service. 

  • To keep in possession or use. 

  • To hold secure. 

topple

verb
  • To totter and fall, or to lean as if about to do so. 

  • To overturn 

  • To overthrow something. 

  • To push or throw over 

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