Bobby vs Willie

Bobby

name

  • A diminutive of the male given name Robert. 

  • A diminutive of the female given name Roberta. 

Willie

name

  • A diminutive of the male given name William 

  • A diminutive of the female given name Wilhelmina or a feminine diminutive of William, often in the form Willie Mae. 

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