past master vs veteran

past master

noun
  • Someone who has previously been a master at a given lodge. 

  • One who has an extremely high level of ability or knowledge within an area of achievement or expertise. 

veteran

noun
  • A person with long experience of a particular activity. 

  • A group, animal, etc. with long experience of a particular activity. 

  • A person who has served in the armed forces, especially an old soldier who has seen long service; also called a war veteran to distinguish from veterans who weren't in armed conflict. 

adj
  • Having had long experience, practice, or service. 

  • Of or relating to former members of the military armed forces, especially those who served during wartime. 

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