post mortem vs posthumous

post mortem

adj
  • Having been inflicted or having occurred after death. 

adv
  • Occurring after death. 

noun
  • An investigation of a corpse to determine the cause of death. 

  • Any investigation after the conclusion of an activity, particularly when said activity produces an unwanted outcome. 

posthumous

adj
  • After the death of someone. 

  • 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. 

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