Phosphorus vs Vesper

Phosphorus

name
  • An Ancient Greek name for the morning star (the planet Venus when it is visible in the eastern sky before sunrise). 

  • A name sometimes used for Hesperus, the personification in Greek mythology of the planet Venus. 

Vesper

name
  • Hesperus, Venus, the evening star 

  • A surname from German. 

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