The contents of this wikibook are out of date and have now moved to http://wiki.objectstyle.org/confluence/display/WO/Home.
WebObjects was initially created at Next. There was a framework called DBKit, which provided a way to abstract legacy databases to an object-relational graph. This framework later became the Enterprise Objects Framework.
EOF was used to build nibware, runnable applications for NextStep/OpenStep that were built with Project Builder and which used interfaces that were designed in Interface Builder. If this sounds familiar, it is because the ideas from that time have only been refined, and not fundamentally changed, to become the Cocoa frameworks for applications running on Mac OS X today.
WebObjects was built on top of DBKit/EOF to provide a way to create applications for the World Wide Web. The first versions of WebObjects were created at Next around the latter half of 1992.
(This information can be fleshed out and corrected when the information from the 2007 WWDC is more widely available.)