Ski Doo vs snowmobile

Ski Doo

snowmobile

verb
  • To ride or race in a snowmobile. 

noun
  • A vehicle with skis at the front and a caterpillar track at the rear, used for travelling over snow, sometimes as sport. 

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