pastry bag vs piping bag

pastry bag

noun
  • A flexible bag from which icing is forced through a small nozzle to make various designs of piping. 

piping bag

noun
  • A cloth bag shaped like a cone with a small hole at the tapered end, used with a metal (or similar) nozzle for squeezing out decorative icing and other pastes in cooking. 

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