go-cart vs hardtop

go-cart

noun
  • A small, open-wheeled vehicle for racing; often spelled go-kart. 

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. 

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