popcorn vs popped corn

popcorn

noun
  • A snack food made from corn/maize kernels popped by dry heating. 

  • A kind of stitch similar to a bobble. 

  • A type of maize with a hard outer hull that, along with the type of starch it contains, makes it suitable for popping. 

  • Entertainment. 

verb
  • To stand or jump up quickly. 

popped corn

noun
  • popcorn. 

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