shale vs slate

shale

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

  • A shell or husk; a cod or pod. 

verb
  • To take off the shell or coat of. 

slate

noun
  • A fine-grained homogeneous sedimentary rock composed of clay or volcanic ash which has been metamorphosed so that it cleaves easily into thin layers. 

  • An artificial material resembling slate and used for the same purposes. 

  • A list of affiliated candidates for an election. 

  • A record of money owed. 

  • A tablet computer. 

  • A thin plate of any material; a flake. 

  • The bluish-grey colour of most slate. 

  • A chalkboard, sheet of slate for writing on with chalk or with a thin rod of slate (a slate pencil) formerly commonly used by both students and teachers in schools. 

  • A roofing-tile made of slate. 

adj
  • Having the bluish-grey/gray colour of slate. 

verb
  • To cover with slate. 

  • To schedule. 

  • To criticise harshly. 

  • To set a dog upon (a person). 

  • To anticipate or strongly expect. 

  • To nominate, appoint, or designate. 

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