Much has been forked, federated here on Hypercard - it was clearly an influence on the development of the web.
But, and sounding obvious since the inventor federates among us, the first wiki was a HyperCard Stack, as spelled out on the C2 wiki link 
Ward Cunningham saw it when still known as WildCard. After playing with its abilities he wanted to explore it as a means to track ideas at his company, Tektronix. The structure created card with three fields, a name, description, and a field for links, the latter "with a twist":
"Stacks were already easy to edit. The fields were automatically WYSIWYG editors. But linking was a pain that involved moving between both cards involved. My Links field abandoned regular stack links and used search on demand instead. Operationally, one would just type links they might follow in the Links field. Each line had a button nearby that would take you to the card if it existed or beep otherwise. If you held the button down, it would relent and go make the card for you."
Here was the idea of the wiki that you could have the system create a link first for something that did not exist, and the system would then make that thing.
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If you think about it (and I'm about to get really meta here) the "search by name" of wiki was kind of the mirror solution of Berners-Lee's "search by location". In both cases, a linked object was abandoned for a blind jump, in an attempt to allow different types of organic growth. -- Mike Caulfield