Too much info, but interesting if you're into mechanical assembly -- for all the fellers and fellerettes who have helped me out in the past and future....

https://en.wikipedia.org/wiki/Keps_nut ...
A Keps nut, (also called a K-nut or washer nut), is a nut with an attached, free-spinning washer. Keps is a trademark of ITW Shakeproof. The name comes from "kep" in Shakeproof, and the "s" is because usually more than one are purchased. It is used to make assembly more convenient. Common washer types are star-type lock washers, conical, and flat washers."

http://www.boltscience.com/pages/glossary.htm ...
SEMS
A screw and washer assembly. A screw or bolt which has a captive washer. The washer is frequently loose on the plain shank of the fastener, the shank diameter being equal to the effective diameter of the thread; the thread being rolled from this diameter. The origin of the word is a frequent question. In the 1930's E. C. Crowther was a representative for a company that sold both shakeproof washers and screws. He came up with the idea of placing the washer on the screw before it was thread rolled. The major diameter of the screw being larger than the washer hole prevents it from coming off. The Illinois Tool Works made machines that produced these patented pre-asSEMbled washers and screws. The s at the end of SEMs is thought to have been subsequently picked up because they are not usually purchased individually. In spite of the original patents and trademarks the word SEMS is generally recognised as a generic term applicable to screw and washer assemblies.

From http://shakeproof.itwautomotive.com/itw-press-room/
ITW is a diversified manufacturer of highly engineered components and industrial systems with $16 Billion in revenues. ITW Shakeproof was formed in 1923 upon the invention of the Shakeproof twisted tooth lockwasher. Over the last 86 years, Shakeproof inventions have become industry standards such as KEPS nuts and SEMS screws. ITW Shakeproof currently offers a full range of internally and externally threaded metal fasteners across a broad size range.

Illustration from another ITW patent:
The exemplary nut (20) of FIGS. 5 and 7 includes a washer (24) assembled therewith. In other embodiments, the nut does not include the slots or washer.

Patent illustration:
http://tinyurl.com/keps-nut-figure-5
or
http://www.google.com/patents/US6726420

And that's my book report for the week...