re- vs retro-

re-

prefix
  • back, backward 

  • again, anew 

  • a completive or intensification of the base; up, a-, out 

retro-

prefix
  • Back or backward. 

  • Behind. 

  • Pertaining to an earlier time. 

  • In the opposite direction. 

  • Old-fashioned or old school. 

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