fly-by-night vs tarpan

fly-by-night

noun
  • A creature which flies at night; a nocturnal flier or traveler. 

  • A traveling businessman or tradesman. 

  • A person or business that appears and/or disappears rapidly, appearing untrustworthy, or giving an impression of transience. 

  • One who departs or flees at night in order to avoid creditors, law enforcement etc. 

tarpan

noun
  • An extinct Northern European wild horse, Equus ferus ferus. 

How often have the words fly-by-night and tarpan occurred in a corpus of books? (source: Google Ngram Viewer )