As an employee of the Western Union Telegraph Company, W. L. Matteson was familiar with the rich vocabulary of insults that telegraph line operators had developed over the years, including, as noted in this article, "lid" and "ham" to describe incompetents. However, at the time this letter appeared popular usage was changing, and many amateur radio enthusiasts had already begun to use "ham" as a casual general description for their fellow amateurs. (In contrast, referring to amateurs as "lids" continues to this day to mean that you are questioning their basic competency.)
QST, December, 1919, page 29:

Denver, Colo., Oct. 22, 1919.
Editor QST:--
    Herewith enclosed is a suggestion on which I would like to hear the opinions of others in your magazine.
    Ever since the earliest days of wireless, the many men and boys who have undertaken to build their own sets or to operate any set, whether for pleasure or for experimental purposes, that did not come under the classification of Commercial or military work, have been termed "amateurs".
    In all other lines of work, "amateur" means one who is either learning or is not proficient in his work. Now can the people that are daily experimenting and operating their own sets be rightfully called amateurs? Hundreds of men and boys have sets that commercial companies might envy. Again, hundreds more can operate their sets every bit as efficient as the man in the land stations, ship stations, in the military and Naval Forces of the world, men who are termed "Radio Operators" in fact many commercial operators could well take lessons from some of our leading amateurs in operation of radio sets.
    Really now, are these so called amateurs, amateurs in the true sense of the word?
    An average outsider hearing the word "amateur" applied to somebody in the wireless game, naturally concludes that this person is a beginner, and looks upon him as a "nut".
    Many unknowing land wire telegraphers, hearing the word "amateur" applied to men connected with wireless, regard him as a "ham" or "lid".
    "Ham"! Possibly, but not probably. Men who can show many of them up when it comes to receiving signals through static and other interference which corresponds to working a "bad wire" in land telegraphy. Men who can send signals twice as clear and readable as some of the land operators can send their Morse. Men who understand the technicality of wireless and the working of their sets and the subject of wireless in general. Whereas, nine out of every ten land wire telegraphers in this country do not even know the fundamentals and working of a simple duplex set, or a single wire repeater. Yet these wireless men are termed "amateurs" because they operate their own stations, and therefore the land wire man has a right to think this radio man is a "ham".
    I am speaking of the more advanced men in the game; men who have studied the subject thoroughly and are experienced in the operation of their sets; not necessarily the eleven year old boy who has just taken it up and has a set consisting of a tuning coil, mineral detector and an old telephone receiver. These boys are true amateurs of course but with an average amount of study and experimenting will soon get out of that class.
    Many men, previously Naval and Military wireless men, are coming back from the war and are putting up their own stations for experimental purposes and for pleasure. Are these men who have worked in some of the complex radio stations of the world to be called "amateurs"?
    I, for one, favor the abolition of the word "amateur" used in connection with the wireless men of this country who own and operate their own sets.
    What are opinions of others on the subject?
W. L. Matteson.      
Multiplex Plant Dept. W. U. Tel. Co.