The first ever wiki site was created on the 25th of March, 1995 as an automated supplement to the PortlandPatternRepository (see History). The site was immediately popular within the pattern community, largely due to the newness of the internet and a good slate of InvitedAuthors. The site was, and remains, dedicated to PeopleProjectsAndPatterns.
WardCunningham created the site and his WikiWikiWeb machinery that operates it. He chose wiki-wiki as an alliterative substitute for quick and thereby avoided naming this site quick-web. An early page, WikiWikiHyperCard, traces wiki ideas back to a HyperCard stack he wrote in the late 80's.
The term wiki that is used to refer to other similar groups of modifiable web pages, like this here, came from that original wiki. Regarding the creation of the word "wiki", see Ward Cunningham's Correspondence on the Etymology of Wiki.
See also one of these links:
get some answers on the WikiWikiWebFaq
get to know more about the WikiHistory