cicerone vs convoy

cicerone

noun
  • A guide who accompanies visitors and sightseers to museums, galleries, etc., and explains matters of archaeological, antiquarian, historic or artistic interest.. 

convoy

verb
  • To travel under convoy. 

  • To escort a group of vehicles, and provide protection. 

noun
  • The act of convoying; protection. 

  • A group of vehicles travelling together for safety, especially one with an escort. 

  • One or more merchant ships sailing in company to the same general destination under the protection of naval vessels. 

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