Conventual vs opposite number

Conventual

noun
  • A member of one of the two divisions of the Franciscans, following a mitigated rule, the other being the Observants. 

opposite number

noun
  • A person who holds a position in an organization that corresponds to that held by another person in another organization; a counterpart 

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