1) Anchor 2) Axle insert 3) Backbone 4) Critical element 5) Critical structural piece 6) Crucial unifying element 7) Exclusively Anglo word 8) Exclusively Saxon word 9) Keystone 10) Lynchpin 11) Mainstay 12) Support 13) Word of purely Anglo origin 14) Word with Anglo-Saxon origins 1) Anchor 2) Backbone 3) Keystone 4) Lynchpin 
A linchpin, also spelled linch pin, lynchpin, or lynch pin, 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 14th century and derives from Middle English elements meaning `axletree pin`. Securing implements onto the three-point hitch of a tractor is an e.....
person or thing vital to an organization
• (n.) A pin used to prevent the wheel of a vehicle from sliding off the axletree.
The most important person or thing in a business or organisation
Linch'pin` (lĭnch'pĭn`) noun [ Anglo-Saxon lynis the axletree; akin to Dutch luns linchpin, Old Saxon lunisa , LG. lunse , German lünse , Old High German lun peg, bolt.] A pin used to prevent the wheel of a vehicle from sliding off the axletree....
[n] - pin inserted through an axletree to hold a wheel on
lynchpin noun pin inserted through an axletree to hold a wheel on