In the Ubuntu 8.04 repository the F is unknown for the FVWM window
manager. I have read before than many don't seem to know what the F in
FVWM (F(?) Virtual Window Manager) stands for. I came across this
screenshot of QNX (see attached file) that has a port of FVWM, and
they refer to it as Franks Virtual Window Manager. I also include the
source URL of where I got the screenshot.