colter vs razor blade

colter

noun
  • A knife or cutter attached to the beam of a plow to cut the sward, in advance of the plowshare and moldboard. 

  • The part of a seed drill that makes the furrow for the seed. 

razor blade

noun
  • A thin piece of steel with a sharp edge that can be fitted into a razor. 

  • A replaceable cartridge in which razor blades are set, fitted into a razor. 

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