The true reason why an amateur radio operator is called a 'ham' is not known - the truth has been lost to the past ages. Various speculations do exist, however - each with a Some degree of believability. Here are the most common. (Presented in no particular order or preference.)

The three letters (H.A.M.) Refer in homage to the initials of the last names of three great radio experimenters. HERTZ, who 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.

Similar to this name and initials connection comes this theory:

It is the combination of the initials of the last names of three Harvard students who supposedly had an amateur station in the early nineteen hundred and teens. Their names were supposedly HYMAN, ALMAY, and MURRAY, and they operated the little amateur radio station with a call sign of "HAM".

This was in a time when any legal administration, red tape or actual assigned callsigns were in their infancy. The three young men were merely identifying their station as "theirs" by using their names "H.A.M." Shortly after the fledgling station emerged, the government DID start proceedings to license and administrate the control all these amateur radio operators which were springing up across the nation. In addition, the government was attempting to gain control and administration of the entire radio wave spectrum. Early amateurs had quite a fight to maintain any radio spectrum for their experiments. Supposedly, an impassioned speech was made on the floor of the US Congress in behalf and support of amateur radio operators and their stations. The "little station that could" (HAM) became the "example of amateur’s experimental endeavors nationwide. The early fight threatened to eliminate all amateur radio stations (by placing all radio under the control of the Navy). This congressional speech citing the little "HAM" station, supposedly turned the tide and defeated the bill that would eliminate amateur radio.

The problem with this theory is that an exhaustive search of the Congressional Record turns up no such speech, and the Harvard School has no record of the Amateur Radio station called "HAM". However, The accuracy and inaccuracies of the Congressional Record in the early part of this century makes it a dubious tool for proof or disproof. Before reforms were enacted in this century, the rules of Congress were very lax. Enough so, that just about anything could be "read into the record" by any member - - whether it was actually SAID on the floor of Congress or not. Likewise members of Congress who knew the "right people" and had enough "pull", could have certain NON-ESSENTIAL items REMOVED from the record, under the guise of shortening an already impossibly large document. The potential here for mis-use and abuse is obvious. Many members of Congress could appease their constituents and special interests by claiming to have made an impassioned plea for their cause on the floor, and pointed to the "Congressional Record" as proof. This led to many obviously ridiculous [documented] paradoxes on "matters of record," such as speeches made by members days or weeks AFTER they boarded a plane or boat which crashed or sank, killing them.

Drawing from the government control theory above, and in an attempt to EXPLAIN the technical radio and electronic matters to the non-technical congress and general public, here is yet another version..

During the earlier days of radio communication, the government stepped in to control frequency allocation of these new "short-waves", and allowed radio amateurs to operate only on certain frequencies scattered in an among the other "authorized" frequencies. Thus, the frequencies of Amateur Radio stations were said to be sandwiched "like the HAM in a sandwich" between the other frequencies, and so Amateur Radio frequencies came to be called the "HAM" portions of the band.

Another theory attributes the term "HAM" to:

Hugo Gernsback, publisher of a magazine called "Home Amateur Mechanic" in the early days of radio. Although it was primarily more mechanical in content, it did contain from time to time, Amateur Radio construction projects. Thus when asked what sort of radio a person had, the reply, more often than not, was he: "had one of those H.A.M. radios" (using just the initials of the well known magazine name)

This became especially believable when you consider the Morse code practice of using just initials or letters for many commonly understood words in order to shorten transmissions and ease sending of messages.

Some speculate the term "HAM" stands for "Help All Mankind" as reflected in the radio amateur’s service towards people in distress during natural calamities, disasters and civil emergencies.

Others believe the term "HAM" derives it’s origin from the late nineteenth-century. English sports writers slang term for any amateur (in sports) was "am" (pronounced with an almost silent "H"). It first came into the "electronics arena" from the "wire-telegraphers" used by these sports writers. The telegraph operators originally applied it to "cub reporters" or neophyte sports writers, who provided sometimes illegibly written or poorly worded copy for them to transmit.

These professional news telegraphers had beginners and neophytes in their own line of work, however, and oftimes the inexperienced new telegraph operators were called "HAMS", for the amateurish way they sent messages. That theory is further explained in the following account...

This theory holds that the term "HAM" actually derives from what the seasoned commercial telegraph operators called the hobby amateur radio operators. When the inexperienced hobby radio enthusiasts began to venture on air with crude spark-gap transmitters, based on vehicle ignition coils, their Morse code transmission must have been pretty poor compared to the commercial telegraphs of the day. The commercial operators referred to the amateurs by using the old telegrapher's insult of "ham fisted", meaning that they weren't of professional skill. "Ham Fisted" referred to their style and proficiency of sending Morse code which could have been done just as well by using a ham (cut of pork) on the telegraph key.

Along those same lines of thought, came this theory linked to the stage and theater. "HAM" connotes a meaning of "unprofessionalism." It came from the theatre where it is used to denote an actor of indifferent ability, or one who shows off his skill or lack thereof, oblivious to his own ineptitude.

The following theory seems to combine the "ham fisted" and the "un-professional operator" theories from above, but also adds a bit more insight as to why amateur radio operators might be called "HAMS"

Ham: a poor performer. [in this case:] An operator of poor performance and courtesy. Even before wireless radio, that's the gist of a definition of the word given in the G. M. Dodge book "The Telegraph Instructor." The definition never changed throughout wire telegraphy history. The first WIRE-LESS operators were landline (wire) telegraphers who left their offices to go to sea or to man the coastal stations. They brought with them their slang terms, and much of the tradition of their older profession. In those early days, spark-gap transmission was king, in fact the only type of transmission readily available, and every station occupied the same wavelength - or, more accurately perhaps, every station occupied the whole spectrum with its broad spark signal. Government stations, ships, coastal stations and the increasingly numerous amateur operators all competed for signal supremacy in each other's receivers. Many of the amateur stations were very powerful. Two amateurs, just working each other across town, could effectively "jam" all the other operators in the area. When this happened, the frustrated commercial operators would telegraph the ship whose weaker signals had been blotted out by the amateurs and say "SRI OM THOSE #&$!@ HAMS ARE JAMMING YOU." ("Sorry old man, those (expletive deleted) hams are jamming you’). The amateur radio operators, possibly unfamiliar with the REAL meaning of the derogatory term "HAM", picked it up and applied it to themselves in true "Yankee Doodle" fashion and wore it with pride. 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. However consider this: There was an English professor back at UMD who pointed out that "bad" or "insulting" words sometimes fall into a period of disuse, and that disuse cause them to become obscure, setting the stage for them to be (ironically) resurrected with more polite, or merely self-deprecating, meanings. Consider, for example, the word "naughty." In Shakespeare's time, it directly translated as "evil" or "demonic," and therefore fell out of polite usage. 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. To be considered a "good ham" is just about the highest mark of honor there is.