posthumous vs prehumous

posthumous

adj
  • In reference to a work, published after the author's death. 

  • Taking place after one's own death. 

  • Born after the death of one's father. 

  • After the death of someone. 

prehumous

adj
  • Before death. 

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