A homey's handshake in the German heartland?

After an enormous water spill on my laptop, the blog is back. Fortunately, everything dried out without causing problems.

Coming back from the Bodensee we passed through a small German town and I saw two high school age girls greeting each other. They did so with a TV handshake. First, they shook hands, then they made fists and knocked them together. It looked incredibly out of place and stupid. It was a homey's handshake brought to the German heartland. They, undoubtedly, had learned it from TV and had no idea where the handshake originated from and what it might mean. It was copied because it looked cool.