profound vs unplumbable

profound

adj
  • Very deep; very serious 

  • Intellectually deep; entering far into subjects; reaching to the bottom of a matter, or of a branch of learning; thorough 

  • Characterized by intensity; deeply felt; pervading 

  • Descending far below the surface; opening or reaching to great depth; deep. 

  • Bending low, exhibiting or expressing deep humility; lowly; submissive 

unplumbable

adj
  • Not plumbable; unfathomable. 

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