quay vs wharf

quay

noun
  • A stone or concrete structure on navigable water used for loading and unloading vessels; a wharf. 

verb
  • To land or tie up at a quay or similar structure, especially used in the phrase "quay up". 

wharf

noun
  • A man-made landing place for ships on a shore or river bank. 

  • The bank of a river, or the shore of the sea. 

verb
  • To place on a wharf. 

  • To secure by a wharf. 

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