hardtop vs motor car

hardtop

noun
  • The removable rigid roof of a convertible or sports car. 

  • An indoor cinema with a roof, as opposed to a drive-in. 

  • A car with such a roof. 

motor car

noun
  • Synonym of railcar. 

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