clear up vs shale

clear up

verb
  • To clean up. 

  • To depart or disappear. 

  • To clarify, to correct a misconception. 

  • To become free of certain blemishes. 

  • Of stormy weather, to dissipate, to become calm. 

  • To pot all of the remaining balls in a single turn. 

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