So how old it is exactly cannot be said, but it is much more a song of opposition to power than of anything else
Right, Wolfgang. It is a song about the outcasty - as wrote above: gypsies.
I don't think that it originated in anarchistic circles. It has the true ring of the romantic "Buendische Jugend" - not boy scouts nor Wandervogel, but somewhere in between.

Why were such songs adapted by the Hitlerjugend? Not only because they had no own songs but: when first founded the HJ was in strong competition with other youth organizations, and to attract the youngsters (age 12 - 16 yrs old) they had to give what their competitors gave: camps, campfires and the right songs. The wild bunch of comrades is undoubtedly more attractive than the official Vorwaerts, vorwaerts, schmettern die hellen Fanfaren (= Onward, onward, the clear clarions are blaring, written by B. v. Schirach, Imperial Youth Leader). Only after 1933 all other youth organizations were forbidden (some of them surviving in the underground) and the HJ remained the one and only youth organization.