Two amateurs, just working each other across town, could effectively jam all the other operators in the area. As the years advanced, the original meaning completely disappeared. These past few derogatory theories may well be close to the true origin of the term, but it seems unlikely that amateurs would willingly adopt a term meant to be insulting to them as their name. In current usage, it's much more benign, and often used to good-naturedly scold friends or children. It would not be implausible then, for what started out as an insult to later become adopted by the target group as a self-deprecating nickname to be worn with pride.
Amateurs view their appellation with considerable pride.
I am often asked how radio works. Well, you see, wire telegraphy is like a very long cat. You yank his tail in New York and he meows in Los Angeles. Now, radio is exactly the same, except that there is no cat.