grind down vs repress

grind down

verb
  • To weaken someone's morale over a long period. 

  • To make something hard smaller and smoother by gradually rubbing off tiny bits, to wear down. 

repress

verb
  • To forcefully prevent an upheaval from developing further. 

  • To check; to keep back. 

  • To press again. 

noun
  • A record pressed again; a repressing. 

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