Middle English lynspin, compound of lins (“axletree”) and pin, from Old English lynis (“linchpin”), from Proto-Germanic *luniso (compare German Lünse), from Proto-Indo-European (compare Welsh olwyn (“wheel”), Old Armenian ողն (ołn, “back; spine, backbone”), Sanskrit आणि (āṇí, “linchpin”)). Figurative use attested from the mid-20th century.
linchpin (plural linchpins)
- a pin inserted through holes at the end of an axle, so as to secure a wheel
- (figuratively) a central cohesive source of stability and security; a person or thing that is critical to a system or organisation.