Base of compiled Microsoft online help (HTMLHelp and Help2) is a set of HTML files created by text editor or tools like FrontPage or Macromedia MX.
It's hard work to think about synonyms the user is looking for and making a good index. Best idea is to do that when writing contents, by giving a good title and keywords that allowed by W3C. Metadata are also conceivable following the example of the "Dublin Core". So you can do this with most HTML editors.
Shareware tools like FAR are using the complete contents of a <title> tag to generate a index and don't output single words for index of help files. A single word index is quite familiar to everyone, having been employed in the back of reference and trade books practically since the beginning of print.
Because users look more to single words the idea to KIT was born.