cobber vs old boy

cobber

noun
  • A pal, buddy, mate, friend; often used in direct address by one male to another. 

  • A sweet consisting of a small block of hard caramel covered in chocolate. 

old boy

noun
  • A former member of a group. 

  • An alumnus, especially of a public school. 

  • An old man. 

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