Actually, nobody knows for certain. The playing style where they use their front feet a lot is one theory, but it's also a fairly modern one

Given that you're talking about a German dog developed almost entirely outside the English-speaking world though, I think it's probably rather
unlikely that they elected to name it after the English word for how the dog plays
Early descriptions of the dog was as a "box" dog. Another of the theories as to how it was named is that the dog was carried around in a box at the rear of carriages - hence "box" or "boxer" dog. They're all just theories though. Those who developed the breed didn't actually write down the reasons they elected to give it the name they did
