oracle vs past master

oracle

noun
  • A fortune-teller. 

  • A wise sentence or decision of great authority. 

  • The sanctuary, or most holy place in the temple; also, the temple itself. 

  • A shrine dedicated to some prophetic deity. 

  • One who communicates a divine command; an angel; a prophet. 

  • A third-party service that provides smart contracts with information from the outside world. 

  • A prophetic response, often enigmatic or allegorical, so given. 

  • A person considered to be a source of wisdom. 

  • A theoretical entity capable of answering some collection of questions. 

  • A person such as a priest through whom the deity is supposed to respond with prophecy or advice. 

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. 

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