concerning vs re

concerning

adj
  • Causing concern; worrying. 

noun
  • That which one is concerned in; one's business. 

prep
  • Regarding, respecting. 

re

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

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

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