impenetrable vs packed

impenetrable

noun
  • A person not openly given to friendship. 

adj
  • Opaque; obscure; not translucent or transparent. 

  • Not penetrable. 

  • Incomprehensible; fathomless; inscrutable. 

packed

adj
  • Filled with a large number or large quantity of something. 

  • Filled to capacity with people. 

  • Put into a package. 

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