Serpent vs Snake Island

Serpent

name
  • Serpens (constellation) 

Snake Island

name
  • Any of several islands with the name 

  • An island in Budjak, on the Black Sea, at the Danue Delta, Danube River in Odessa Oblast, Ukraine, on the border with Romania 

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