detach vs shale

detach

verb
  • To take apart from; to take off. 

  • To separate for a special object or use. 

  • To come off something. 

shale

verb
  • To take off the shell or coat of. 

noun
  • A shell or husk; a cod or pod. 

  • A fine-grained sedimentary rock of a thin, laminated, and often friable, structure. 

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