extrude vs shale

extrude

verb
  • To expel; to drive off. 

  • To push or thrust out. 

  • To form or shape (a metal, plastic etc.) by forcing it through a die or an opening. 

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 extrude and shale occurred in a corpus of books? (source: Google Ngram Viewer )