Diagonal vs Serpentine

Diagonal

name

  • A city and town in Iowa. 

Serpentine

name

  • A river in Canada. 

  • A river in New Zealand. 

  • The lake in Hyde Park, London. 

  • A river in Alaska. 

  • A river in Australia. 

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