Yeah, there are many different designations for different types of German artillery.
KwK means kampfwagenkanone or literally vehicle-mounted gun.
FlaK comes from fliegerabwehrkanone or aircraft-defense gun.
PaK from panzerabwehrkanone or tank-defense gun.
SiG from sturminfanteriegeschuetz or assault support cannon,
LeFH from leichteFeldHaubitze or light field howitzer.
Now, I don't want to see anymore wrong designations