[aerohead]

Some will relate the term to the 5-car series developed at FKFS between 1930 and 1941, next door to Daimler Benz.
The 'K' stands for both Professor, Wunnibald I. 'Kamm', who created the FKFS, and Baron Rinehard 'Koenig'-Fachsenfeld, who traded his aerodynamic patents to the German government, in exchange for free use of the FKFS and it's wind tunnel.
The aerodynamic term 'Kamm-back' is a reference to the K-form, of which was the intellectual property of Fachsenfeld.
Germany had lost WW-I, in part, due to running out of oil and rubber.
Adolf Hitler was very interested in stretching Germany's fuel supplies, until he could capture North Africa, the Middle East, Ploesti Romania, and the Soviet's Caspian Sea petroleum. The lower-drag, aerodynamic capabilities of the K-form factored into that calculus as a bridge technology.
It didn't work out very well, and they ended up losing WW-II in part, because of lack of oil and rubber.
You may have seen photographs of GM's Opel Russelsheim factory storage area, full of brand new Blitz Trucks, with wooden wheels, awaiting rubber from I.G. Farben, who's synthetic fuel and rubber factories were ultimately bombed into oblivion by Allied air forces.