obstinate vs on a string

obstinate

adj
  • Stubbornly adhering to an opinion, purpose, or course, usually with implied unreasonableness; persistent. 

  • Typical of an obstinate person; fixed and unmoving. 

  • Not easily subdued or removed. 

on a string

prep
  • Under one's control or influence. 

How often have the words obstinate and on a string occurred in a corpus of books? (source: Google Ngram Viewer )