roadstead vs seaport

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. 

seaport

noun
  • A town or harbour with facilities for seagoing ships to dock and take on or discharge cargo. 

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