mare vs seawater

mare

noun
  • A large, dark plain, which may have the appearance of a sea. 

  • On Saturn's moon Titan, any of several lakes which are large expanses of what is thought to be liquid hydrocarbons. 

  • A nightmare; a frustrating or terrible experience. 

  • A foolish woman. 

  • An adult female horse. 

seawater

noun
  • The saltwater of a sea or ocean. 

adj
  • Associated in some way with seawater, or intended for dealing with seawater. 

  • Consisting of seawater. 

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