Ham was a term likely coined by professional radiotelegraphers to mean ham-fisted (with 'fist' being a term referring to technique used when sending Morse code)

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.

Ham comes from pigs =)

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.

It’s shorthand for amateur radio operator (as opposed to professional, e.g. ship to shore.)

I read something online about it coming from a Harvard callsign. Is that nonsense?

Like a goofy person “hamming it up”

Amateur radio operators can seem undisciplined compared to professional or military operators.