thumb|Wagon wheel, with forged linchpin thumb|A modern linchpin with an integral spring retainer
thumb|Wagon wheel, with forged linchpin thumb|A modern linchpin with an integral spring retainer
A linchpin, also spelled lynchpin, is a fastener used to prevent a wheel or other part from sliding off the axle upon which it is riding. The word is first attested in the late fourteenth century and derives from Middle English elements meaning "axletree pin".
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).