blab vs open one's mouth

blab

verb
  • to speak carelessly or excessively 

  • To tell tales; to gossip without reserve or discretion. 

noun
  • One who blabs; a babbler; a telltale; a gossip or gossiper. 

  • Gossip; prattle. 

open one's mouth

verb
  • to speak 

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