Pseudo-Acronym for "Größter Feldherr aller Zeiten" (greatest battle leader of all times), a title given to Adolf Hitler after his initial military successes by Wilhelm Keitel, chief of the military high command, who was well-known for his ingratiating behaviour towards the Führer.

Although the title fit well with the Führerkult and Hitler himself liked it, its pompousness was already too much for general use. It was turned it into an outright insult by forming the acronym, especially since the contraction "faz" sounds close to fatzke, which mean fop.

I'm nore sure who invented this usage; it must have been some time late in the war, because it wouldn't have worked as long as Hitler-Germany appeared to be winning. It did have the advantage that you could use it without being arrested because you could always claim that it was meant seriously.

The title and the acronym are still in use today as a deriding way to refer to Hitler or other dangerous megalomaniacs (it can be adjusted by substituting "Feldherr" with a word more appropriate to the specific case).