knackwurst vs wienerwurst

knackwurst

noun
  • A highly seasoned scalded sausage made from beef, pork, and fatty tissue similar to a frankfurter, but shorter and thicker. 

wienerwurst

noun
  • Vienna sausage 

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