Linchpin

linchpin
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
3. a person or thing regarded as an essential or coordinating element
Usage
Like a linchpin, the little fastener used to prevent a wheel from sliding off the axle, staff and technical sergeants may not be well-known, but they are indispensable. They are the middle ranks in the enlisted rank structure, essential building blocks of the enlisted force and are often the Air Force’s technical experts.
dvidshub.net
Etymology
also linch-pin, late 14c., earlier linspin, from M.E. lins "axletree" (see linch) + pin (n.). The peg that holds a wheel on an axle; now mainly figurative.

Bumf

bumf
1. Printed matter, such as pamphlets, forms, or memorandums, especially of an official nature and deemed of little interest or importance.
2. Toilet paper.
Usage
So a medical translation is put through the linguistic hoops and the hourly rate reflects the cost; a bunch of bumf for a pamphlet perhaps gets just the once-over.
nzherald.co.nz Jul 23, 2012
Etymology
papers, paperwork," 1889, British schoolboy slang, originally "toilet-paper," from bum-fodder.

Dune

Dune
A ridge of sand created by the wind; found in deserts or near lakes and oceans.
Usage
The driver of a four-wheel-drive adventure bus that rolled in sand dunes near Lancelin last year, leaving tourists with serious spinal injuries has been charged for not having a licence to drive the vehicle.
smh.com.au
Etymology

1790, from Fr. M.Du. or M.L.G. dune, all perhaps from Gaulish *dunom (thus related to down (n.2)). The French word (13c.) is held to be an Old French borrowing from Germanic. Dune buggy attested by 1965.