DM vs PM

DM

verb
  • To communicate by direct message, usually on a social website. 

  • To Dungeon Master; to perform as a dungeon master; to run a tabletop role-playing game. 

noun
  • A Dr. Martens boot or shoe. 

  • driving motor car 

  • Coordinate terms: PM, IM 

  • adamsite, diphenylaminechlorarsine 

PM

verb
  • To send a private message to (a participant in a chat room, etc.). 

  • To project manage. 

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