flank steak vs flap steak

flank steak

noun
  • A beef steak cut cut from the abdominal muscles or buttocks of the cow. 

flap steak

noun
  • A cut of steak from the bottom sirloin, a butt cut, that is thin and lean, with coarse fibre. It is similar to the skirt steak, flank steak, hanger steak, and like those three, also sometimes called a bavette. It is a cut used to provide the meat found in sirloin tips. 

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