thorough vs tip of the iceberg

thorough

adj
  • Utter; complete; absolute. 

  • Painstaking and careful not to miss or omit any detail. 

noun
  • A furrow between two ridges, to drain off the surface water. 

tip of the iceberg

noun
  • A small indication of a larger possibility; the first part encountered of a problem that is much bigger than it seems. 

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