Frank vs Rob

Frank

name
  • A diminutive of the male given name Francis 

  • A male given name from the Germanic languages. 

  • A surname transferred from the nickname. 

noun
  • One of the Franks, a Germanic federation that inhabited parts of what are now France, the Low Countries and Germany. 

Rob

name
  • A diminutive of the male given name Robert. 

  • A surname transferred from the given name, derived from Robert. 

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