gab vs shoot one's mouth off

gab

verb
  • To talk or chatter a lot, usually on trivial subjects. 

noun
  • The mouth or gob. 

  • Idle chatter. 

  • One of the open-forked ends of rods controlling reversing in early steam engines. 

shoot one's mouth off

verb
  • To make reckless or exaggerated statements. 

How often have the words gab and shoot one's mouth off occurred in a corpus of books? (source: Google Ngram Viewer )