claw back vs regain

claw back

verb
  • To recover or retake, with great effort, something that was lost, often by a government or official agency. 

regain

verb
  • To get back; to recover possession of. 

noun
  • The amount of width a woven cloth grows by when the fibers swell, used to determine the width of the reed to use in weaving. 

  • The act or process of regaining something. 

How often have the words claw back and regain occurred in a corpus of books? (source: Google Ngram Viewer )