pliable vs set in stone

pliable

adj
  • Easily persuaded; yielding to influence. 

  • Soft, flexible, easily bent, formed, shaped, or molded. 

set in stone

verb
  • To render something permanent, certain, or firm. 

adj
  • Permanent; certain; firm. 

How often have the words pliable and set in stone occurred in a corpus of books? (source: Google Ngram Viewer )