The codenames for every major Debian release are named after characters from Pixar’s Toy Story franchise. Debian’s unstable release is fittingly named after Sid, an unstable character from the Toy Story movies.
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!)