Mole vs Sow

Mole

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

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

  • A surname. 

Sow

name
  • A river in Staffordshire, England, which joins the River Trent. 

  • A surname. 

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