Keystone vs Mole

Keystone

name
  • A city and town in Iowa. 

  • A town in South Dakota. 

  • A census-designated place in Colorado. 

  • A ghost town in North Dakota. 

Mole

name
  • A river in Devon, England, tributary to the Taw. 

  • A river in Surrey, England, tributary to the Thames. 

  • A surname. 

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