matatu vs share taxi

matatu

noun
  • A minivan used as a share taxi, especially one operating without a licence. 

share taxi

noun
  • A vehicle for hire, typically smaller than a bus, taking passengers on a fixed or semi-fixed route without timetables, departing when all seats are filled. 

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