acquiesce vs speak out

acquiesce

verb
  • To rest satisfied, or apparently satisfied, or to rest without opposition and discontent (usually implying previous opposition or discontent); to accept or consent by silence or by omitting to object. 

  • To concur upon conviction; to assent to; usually, to concur, not heartily but so far as to forbear opposition. 

speak out

verb
  • To assert or promote one's opinion; to make one's thoughts known. 

How often have the words acquiesce and speak out occurred in a corpus of books? (source: Google Ngram Viewer )