quay vs roadstead

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". 

roadstead

noun
  • A partly sheltered anchorage; a stretch of water near the shore where vessels may ride at anchor, but with less protection than a harbour. 

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