songthaew vs tro tro

songthaew

noun
  • A type of share taxi in Southeast Asia made out of an altered pickup truck with two benches in the back down each side. 

tro tro

noun
  • A minibus operating as a share taxi in Ghana. 

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