I emailed the ITW company and got this very nice response back quickly.
Robert,
Prior to the invention of KEPS by the Shakeproof Division of ITW, nuts and washers were assembled by hand as separate components. Usually the washers were of the conical or tooth design. Invariably some washers would not get assembled causing a subsequent joint failure.
At the time, preassembly of the nut and washer into a single component was a major breakthrough in fastener technology. The assembled components not only provided the opportunity for improved automation, but assured that each fastened joint contained a washer. The trademark name KEPS was created by marketing as a short and easy to remember product name. Even today KEPS is a generic term for any pre-assembled nut and washer.
Pictures of various nut and washer assemblies may be viewed at:
www.itwautomotive.com
Hopefully this brief history of KEPS is an adequate response for those curious students you teach. Best regards
Jim Anderson
ITW Shakeproof Industrial Products
Operations Manager
It was quite nice of them to take the time to inform us.