Is the word “Panzer” not slang for “Panzerkampfwagen”? Think about it.
I am no German expert, but I think the exact translation is
Panzer (armored) Kampf (combat) wagen (car/vehicle)
That is correct.
Abbreviation rather than slang.
Same with FLAK - FLiegerAbwehrKanonen
and PAK - PanzerAbwehrKanon
I would think slang though, because an abbreviation is when you take the starting letter for each word (PKW), while slang is shortening a word.
Abbreviation is any shortening. Acronym is a particular type of abbreviation where you take initials.
Slang is any informal usage of language - often inside a particular group of people.
They are not exclusive of each other, so you can think of “Panzer” as both an abbreviation and slang - although it is no longer restricted to a particular group of people!
Flak as a general term for anti-aircraft is also slang, having originated as an official abbreviation.
…like taking flak and flakin hell haha xxx