Just ham, not HAM, not H.A.M.
Amateur radio operators can seem undisciplined compared to professional or military operators.
An early example of elitism in radio that is still very prevalent today - Professionaly trained telegraphy operators talking down amateurs who are involved for the fun of it, for having sloppy technique when sending code.
Put originally it was a pejorative used by professional telegraph operators to make fun of 'ham fisted' amature radio oporators who were bad at morse code.
Source: My father was very active in UK ham radio circles back in the 1980s.