Now, I know you are German, but I must really correct you. Wisecracker 1st class
'Panzer' actually always ment 'armor' in German. When 'armored cars' (aka tank) came, they were referred to as Panzer just because it was convenient (And they were the first heavily armored vehicles).
Panzer also can refer to any body armor - as in, plate armor (
Plattenpanzer)...or even animal's protective shell (as in turtle shell -
Schildkrötenpanzer). It is quite obvious that 'panzer' existed as a word referring to all kinds of armoring long before tanks existed. You think that derivations of 'panzer' like panzerung somehow relate to the armored tanks. It is however hence the reverse...!
Etymology also conclusively shows that panzer is _not_ a tank. Middle High German used the word 'Panzier' which ment armor, or 'armor for the belly' (medieval time).
'Panzerzug' therefor is an ARMORED train, not a tanktrain.