The reason why an amateur radio operator is called a ‘ham’ is not known. Some relate these three letters (HAM) to the names of three great radio experimenters. They are- Hertz (who practically demonstrated the existence of electromagnetic waves in 1888), Armstrong (who developed a resonant oscillator circuit for radio frequency work) and Marconi (the 1909 Nobel laureate in Physics, who in the year 1901 established the first transatlantic radio contact).
Some people believe that when the young and inexperienced radio enthusiasts began to venture on air with crude spark transmitters based on vehicle ignition coils, their Morse code transmission must have been pretty poor and professionals dismissed them as ‘ham fisted’!
While others have their own version; according to them during the earlier days of radio communication, government stepped in to conquer short-waves and allowed the radio amateurs to operate only on certain frequencies; thus the frequencies of amateur radio stations were sandwiched like a ‘ham sandwich’ and so amateur radio operator came to be called a ‘ham’.
Another speculation is that the word “HAM” stands for ” Help All Mankind” as reflected in its service towards people in distress during natural calamities, disasters and civil emergencies!