linchpin vs rivet

linchpin

noun
  • A pin inserted through holes at the end of an axle or shaft, so as to secure a wheel or shaft-mounted device. 

  • A central cohesive source of stability and security; a person or thing that is critical to a system or organisation. 

verb
  • To adopt as, or serve as, a central cohesive source of stability and security. 

rivet

noun
  • A cylindrical mechanical fastener that attaches multiple parts together by fitting through a hole and deforming the head(s) at either end. 

  • Any fixed point or certain basis. 

verb
  • To command the attention of. 

  • To attach or fasten parts by using rivets. 

  • To make firm or immovable. 

  • To install rivets. 

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