famulus vs retainer

famulus

noun
  • A close attendant or assistant, especially of a magician or occult scholar. 

retainer

noun
  • A dependent or follower of someone of rank. 

  • A fee one pays to reserve the other's time for services. 

  • A device that holds teeth in position after orthodontic treatment. 

  • Any thing or person that retains. 

  • A retaining valve. 

  • A paid servant, especially one who has been employed for many years. 

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