flabbergast vs leave openmouthed

flabbergast

verb
  • To overwhelm with bewilderment; to amaze, confound, or stun, especially in a ludicrous manner. 

noun
  • An awkward person. 

  • Overwhelming confusion, shock, or surprise. 

leave openmouthed

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