pier vs sprag

pier

noun
  • A raised platform built from the shore out over water, supported on piles; used to secure, or provide access to shipping; a jetty. 

  • A structure supporting the junction between two spans of a bridge. 

  • A similar structure, especially at a seaside resort, used to provide entertainment. 

  • A rectangular pillar, or similar structure, that supports an arch, wall or roof, or the hinges of a gate. 

sprag

noun
  • A billet of wood; a piece of timber, a similar solid object or constructed unit used as a prop. 

  • A young salmon. 

verb
  • To prop or sustain with a sprag. 

  • To check the motion of, as a carriage on a steep slope, by putting a sprag between the spokes of the wheel. 

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