It seems the origins of the ham radio “Elmer” as a teacher or mentor has been lost over time.
Well maybe just a bit forgotten?
Here is a 1920s Amateur Radio book in its more recent reprint that might offer a clue:
It seems the down to earth writing and persistent mentoring by the author created a name recognition in radio’s early days.
One attribution is:
Elmer E. Bucher (pronounced, ‘boo-cher’) was an instructing engineer at the Marconi Wireless Telegraph Co. of America in the very early pioneering days of radio just after the turn of the Twentieth Century.
Mr. Bucher was a great mentor to thousands of early amateur and professional operators in the fields of wireless telegraphy and radio.
His mentoring was so well known that even today, Radio Amateurs who mentor novices in getting their “Ham” licenses are commonly called, “Elmers.”
His book, PRACTICAL WIRELESS TELEGRAPHY, was published from 1917 to 1920 and covered everything from batteries and magnets to setting up and operating a complete wireless station.
In his own words, “The author has endeavored to give the non-technical student and the practical telegraphist an understanding of the functioning of present day commercial wireless telegraph apparatus” .. [and]… his mentoring so many people in the field of wireless that his name lives on with experienced radio amateurs “Elmering” radio beginners every day.
So perhaps not such a lost origins after all?
Elmer Bucher was well enough known that his obituary ended up in the New York Times.
Seems as good of an explanation for Elmer and Elmering as any others I’ve been told.