The name KDE was intended as a wordplay on the existing Common Desktop Environment, available for Unix systems.[6] CDE was an X11-based user environment jointly developed by HP, IBM, and Sun through the X/Open consortium, with an interface and productivity tools based on the Motif graphical widget toolkit. It was supposed to be an intuitively easy-to-use desktop computer environment.[7] The K was originally suggested to stand for "Kool", but it was quickly decided that the K should stand for nothing in particular. Therefore, the KDE initialism expanded to "K Desktop Environment" before it was dropped altogether in favor of simply KDE in a rebranding effort in 2009.[8]

https://en.wikipedia.org/wiki/KDE

(TIL the creator of KDE studied at the same university as me!)