It looks like "KDE" and "kde" are
both defined several
places in kcmdlineargs.cpp for parsing purposes. Furthermore,
the following files in tdelibs alone use or provide this string in the command
line context:
tdelibs/tdecore/kcmdlineargs.cpp
tdelibs/tdecore/kuniqueapplication.cpp
tdelibs/tdecore/kapplication.cpp
To directly answer your question, the text string itself is
defined in kapplication.cpp:1566, but modifying the text string means
that the other files I mentioned must also be modified.
Hope this helps!
Updated in GIT hash 554196e4. :)
Darrell