"Boilerplate" also refers to the branding plates that were placed on boilers that contained repeated information on every boiler. I think it's more likely the term comes from that.
It's annoying the author isn't on twitter where this could be corrected!
Author here, looking into those earlier sources now
EDIT: The "Advisory Opinions" source is mislabeled and was published after 1989. [1] The "Typographic Journal" refers to boiler plate as a derogative for a low quality newspaper:
> The next city visited was Paris, Ill. which "supports" four newspapers. The only one worthy of mention is the Beacon … The other newspapers thive on "boiler plates" exclusively [2]
Agree "Advisory Opinions" was mislabeled. That's annoying.
My point about "Typographic Journal" is that their usage is quite different - they are using it as a synonym for low quality, not the kind of fill-in-the-blanks usage we see now.
In 1851 "De Bows Review"[1] talks about how it is a felony to use unstamped boiler-plate, conceal the plate on the boiler-plate or counterfeit the stamp. To me that goes to filling-in of boilerplate with details (using the stamp) which seems a more likely origin than the "lower quality" usage used by "Typographic Journal".
This was 20 years before the invention of the linotype machine (1884) that this author claims it was named after.
In 1896 "The Typographical Journal" did use "boiler plate" to refer to the type of printing process, but not to it being a pro-forma piece of information: https://www.google.com.au/books/edition/The_Typographical_Jo...
"Boilerplate" also refers to the branding plates that were placed on boilers that contained repeated information on every boiler. I think it's more likely the term comes from that.
It's annoying the author isn't on twitter where this could be corrected!