Billy vs Duff

Billy

name
  • A diminutive of the male given name William. 

  • The B-25 twin-engine bomber aircraft used during World War Two, commonly called the "B-25 Mitchell" in honor of U.S. Army General William "Billy" Mitchell. 

Duff

name
  • A male given name 

  • An unincorporated community in Tennessee, United States 

  • An unincorporated community in Indiana, United States 

  • A village in Saskatchewan, Canada 

  • A surname. 

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