cherub vs seraph

cherub

noun
  • A winged creature attending God, described by Pseudo-Dionysius the Areopagite (c. 5th–6th century) as the second highest order of angels, ranked above thrones and below seraphim; similar to a lamassu in the pre-exilic texts of the Hebrew Bible, more humanoid in later texts. 

  • A person, especially a child, seen as being particularly angelic or innocent. 

  • An artistic depiction of such a being, typically in the form of a winged child or a child's head with wings but no body. 

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 cherub and seraph occurred in a corpus of books? (source: Google Ngram Viewer )