apropos vs re

apropos

prep
  • Regarding or concerning. 

adv
  • To the purpose; appropriately. 

  • By the way. 

  • Timely; at a good time. 

adj
  • Of an appropriate or pertinent nature. 

  • by the way, incidental 

re

prep
  • About, regarding, with reference to; especially in letters, documents and emails. 

noun
  • a syllable used in solfège to represent the second note of a major scale. 

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