recede vs regrade

recede

verb
  • To take back. 

  • To cede back; to grant or yield again to a former possessor. 

  • To move back; to retreat; to withdraw. 

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 recede and regrade occurred in a corpus of books? (source: Google Ngram Viewer )