Chew vs Thaw

Chew

name

  • A river in Somerset, England 

  • A surname. 

Thaw

name

  • A river in South Wales which flows into the Bristol Channel at Aberthaw. 

  • A surname from Burmese. 

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