From Longman Dictionary of Contemporary Englishlinchpinlinch‧pin, lynchpin /ˈlɪntʃˌpɪn/ noun → the linchpin of something
Examples from the Corpus
linchpin• Divas are often the financial linchpins for opera productions costing hundreds of thousands of dollars.• Dalton Baldwin's linchpin accompaniments are all that one could hope for in terms of grace and humour.• Apparently she accepted that she was the primary caretaker of her children and the linchpin of family life.• Removing the middle would be like removing the linchpin.• Erme was the linchpin of the whole thing.• Consumer goods industries were the linchpin, and these were overwhelmingly located in the West Midlands and in and around Greater London.From Longman Business Dictionarylinchpinlinch‧pin /ˈlɪntʃˌpɪn/ (also lynchpin) noun [singular] the most important thing or person in a system, plan etc, which everything else depends onThe consumer is the linchpin of the economy.Origin linchpin (1300-1400) linch “pin fastening a wheel to an axle” ((11-16 centuries)) (from Old English lynis) + pin 