regrade vs retake

regrade

noun
  • The act or process of grading again. 

verb
  • To regroup or reassign. 

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

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

retake

noun
  • an instance of resitting an examination 

  • a scene that is filmed again, or a picture that is photographed again 

verb
  • To take something again. 

  • To capture or occupy somewhere again. 

  • To photograph or film again. 

  • To take something back. 

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