back down vs regrade

back down

verb
  • To take a less aggressive position in a conflict than one previously has or has planned to. 

  • To withdraw from a commitment or position. 

regrade

verb
  • To regroup or reassign. 

  • To change the classification of (potentially secret documentation). 

  • To grade again, give a new grade or grading to. 

noun
  • The act or process of grading again. 

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