frozen yogurt vs gelato

frozen yogurt

noun
  • A frozen dessert made from yogurt or other dairy products, slightly tarter than ice cream and lower in fat. 

gelato

noun
  • An Italian variant of ice cream made from milk and sugar, combined with other flavourings. The ingredients are supercooled while stirring to break up ice crystals as they form. 

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