flip side vs verso

flip side

noun
  • The reverse, in contrast to the obverse. 

  • The converse; opposite, usually negative, inherent aspects or consequences of something. 

verso

noun
  • The left-hand page of a book of a script which reads from left to right, usually having an even page number. 

  • The back side of a flat object which is to be examined visually, as for reading, such as a sheet, leaf, coin or medal; 

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