motor scooter vs roller skate

motor scooter

noun
  • A small motorcycle or moped with a step-through frame. 

roller skate

noun
  • A boot having small wheels or casters attached to its sole; used for roller skating. 

verb
  • To skate using roller skates. 

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