For a long time udoc was called qdoc. Because Trolltech might want to release its qdoc (abbreviated from
qt doc tool for no particularly good reason), it seemed sensible to rename this one before release. A simple matter — just step along to the next letter, I thought. But then there turned out to be something called rdoc already. And two programs called sdoc. tdoc was taken too. A few quick searches showed that there are more than 26 programs like udoc.
You can understand why I considered naming it fdoc.