Linchpin - Wikipedia, the free encyclopedia - http://en.wikipedia.org/wiki...
May 23, 2011
from
"A linchpin, also spelled linch pin, lynchpin, or lynch pin, is a fastener used to prevent a wheel or other rotating part from sliding off the axle it is riding on. The word is first attested in the 14th century and derives from Middle English elements meaning "axletree pin""
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