cup of joe vs joe

cup of joe

noun
  • A cup of coffee. 

  • One’s personal preference. 

joe

noun
  • Coffee. 

  • Synonym of johannes (“An old Portuguese gold coin bearing a figure of John V of Portugal.”) 

  • A spy, especially a double agent. 

  • A male; a guy; a fellow. 

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