Estuary vs Sound

Estuary

name
  • Estuary English 

Sound

name
  • Synonym of Plymouth Sound, Devon, England. 

  • The strait that separates Zealand (an island of Denmark) from Scania (part of Sweden); also sometimes called by the Danish name, Øresund. 

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