once more vs re-

once more

adv
  • Used other than figuratively or idiomatically: see once, more. 

  • Again, a further time, once again. 

re-

prefix
  • back, backward 

  • again, anew 

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

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