Ally vs Tiff

Ally

name
  • A diminutive of the female given names Alice, Alison, Alexandra, or other names beginning with Al-[[#English|]], from the Germanic languages or Ancient Greek 

  • A diminutive of the male given names Alfred, Albert, Alan, Alexander, or other names beginning with Al-[[#English|]], from the Germanic languages, the Celtic languages, or Ancient Greek 

Tiff

name
  • A diminutive of the female given name Tiffany. 

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