I know that early catalogs, price lists, and even box labels don't use the term, but at some point the company had to brag about the superiority of this model's obvious value-added feature. There have to be references in design documents as early as (I guess) 1905 and in commercial announcements through the years that preceded the model's retirement. How did the people who knew what they were building refer to the model when they wrote interoffice memos about it? How did they talk about it correspondence with their retailers and distributors?
Let's not lose sight of the fact the hyphenated form "Triple-lock" has also been frequently seen and used. In the now-retired Yahoo-based SWCA firearm database, it was the parenthetical term inserted after the main description ".44 HE, 1st Model." The compilers of the Standard Catalog of Smith & Wesson use "Triple Lock" in the section heading for their discussion of the model, and use the hyphenated form with varying capitalization in the following text. The authors of Smith & Wesson: 1857-1945 used "Triple Lock" in their section head and then specifically referred to "the nickname Triple Lock" in their write-up.
In recognition of the TL's superior and almost divine realization of engineering stability, I think it might also have been called "The Revolver of The Threefold Way." But I anticipate no success in persuading anyone to adopt that new nickname, so I will only mention it and refrain from making a formal proposal.