linch·pin or lynch·pin (lĭnchpĭn′)
1. A locking pin inserted in the end of a shaft, as in an axle, to prevent a wheel from slipping off.
2. A central cohesive element: Reduced spending is the linchpin of their economic program.
[Middle English linspin : lins, linchpin (from Old English lynis) + pin, pin (from Old English pinn; see PIN).]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.