low gear vs low-water mark

low gear

noun
  • The lowest gear available from a gearbox, typically in a motor vehicle or cycle. 

  • One of the lower gears available from a gearbox, typically in a motor vehicle or cycle. 

low-water mark

noun
  • The nadir or lowest point of something. 

  • A mark, such as a line of seaweed, showing the lowest level reached by a body of water. 

How often have the words low gear and low-water mark occurred in a corpus of books? (source: Google Ngram Viewer )