clabbered vs impenetrable

clabbered

adj
  • Thickened or curdled. 

impenetrable

adj
  • Opaque; obscure; not translucent or transparent. 

  • Not penetrable. 

  • Incomprehensible; fathomless; inscrutable. 

noun
  • A person not openly given to friendship. 

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