fallen angel vs seraph

fallen angel

noun
  • An angel who rebelled against God and was exiled from heaven. 

  • A (usually attractive) person, usually a woman, who has become deprived of money, status or morals. 

  • A bond that has declined in value due to credit deterioration to become a junk bond. 

seraph

noun
  • A six-winged angel; one of the highest choir or order of angels in Christian angelology, ranked above cherubim, and below God. They are the 5th-highest order of angels in Jewish angelology. A detailed description can be found at the beginning of Isaiah chapter 6. 

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