shallow vs tip of the iceberg

shallow

adj
  • Not steep; close to horizontal. 

  • Not far forward, close to the net. 

  • Having little depth; significantly less deep than wide. 

  • Not intellectually deep; not penetrating deeply; simple; not wise or knowing. 

  • Concerned mainly with superficial matters. 

  • Extending not far downward. 

  • Lacking interest or substance. 

noun
  • A costermonger's barrow. 

  • A shallow portion of an otherwise deep body of water. 

  • A fish, the rudd. 

verb
  • To make or become less deep. 

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 shallow and tip of the iceberg occurred in a corpus of books? (source: Google Ngram Viewer )