minibus vs motor coach

minibus

noun
  • A small four-wheeled carriage. 

  • A small bus, especially one used as transport for small groups. 

  • A sixteen-seater vehicle used as a taxi. 

  • A combined spending bill for multiple departments that is smaller than an omnibus bill. 

motor coach

noun
  • A powered railway vehicle, designed for passenger transport, capable to pull (or push) other railroad cars (compared to a railcar which only consists of a single railway vehicle with a driver's cab at both ends). 

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