It's hard to remember this kind of weird random capitalization.
When I read "iPhone", I remember "i, phone, two words with only the second word capitalized".
When I read "mRNA", I remember "mrna, all caps except for the first letter".
When I read it I read "NeXT", I read, "next with random capitalization".
Now when I write back, the first 2 are deterministic; the third is probabilistic.
Are you familiar with McIntosh apples? ;)
The computer industry really jumped into case sensitive naming with both feet. I'm sure NeXT wasn't the first such example but they were one of the earlier ones when it started to become the norm.
I don't know how to judge "when it started to become the norm." It seems too easy to set the line semi-arbitrarily to the time you want.
A Mac users in the 1980s, before NeXT, would know about MacPaint and other Mac* software. The Mac 2D graphics used QuickDraw, which in turn was "was grounded in the Apple Lisa's LisaGraf" (quoting Wikipedia).
MicroPro International Corporation developed WordStar staring in June 1979. Again quoting Wikipedia, "By May 1983 BYTE magazine called WordStar "without a doubt the best-known and probably the most widely used personal computer word-processing program"."
There's AutoCAD.
And in the 1970s and 1980s ComputerLand was a large retail computer store, with "about 800 stores by 1985." (Microsoft, btw, was originally "Micro-Soft".)
While it may have been popular in the computer industry, I don't know enough about other fields. I pointed out in another thread the DryIce Corporation started in the 1920s, producing frozen carbon dioxide.
Edit: I realized I do know of earlier naming schemes which used mixed-capitalization. Before Micro-Soft was "Traf-O-Data", which followed a mid-20th century practice that includes Bridge-O-Rama (https://en.wikipedia.org/wiki/Bridge-O-Rama ) Bowl-O-Rama (http://www.bctv.org/opinion/bowl-o-rama-was-more-than-a-bowl... ), etc.
Just anecdotally, it would seem publications tend to respect camel case but may or may not when there are other capitalization oddities including lowercase first letters.
CiCi's pizza - "Joe Croce and Mike Cole founded Cicis in 1985". (That was also the year NeXT was founded.)
"In 1971, Nebraska Consolidated Mills changed its name to "ConAgra""
"CryoLife, Inc. incorporated in 1984 in Florida, was the first biomedical company to specialize in the ultra-low temperature preservation of human heart valves used for cardiac reconstruction, primarily in children born with heart defects."
Freeport-McMoRan - "In 1981, Freeport Minerals Company merged with the McMoRan Oil and Gas Company. The McMoRan Oil and Gas Company was founded in 1967 by three partners, William Kennon McWilliams Jr. ("Mc"), James Robert (Jim Bob) Moffett ("Mo"), who were both petroleum geologists, and Byron McLean Rankin, Jr. ("Ran"), ..."
BankAmericard - founded in 1958; became Visa. "In June 1970, Bank of America gave up control of the BankAmericard program. The various BankAmericard issuer banks took control of the program, creating National BankAmericard Inc. (NBI), an independent Delaware corporation which would be in charge of managing, promoting and developing the BankAmericard system within the United States."
"In 1965, the Pepsi-Cola Company merged with Frito-Lay, Inc. to become PepsiCo, Inc"
"Initially held as a private partnership, SeaWorld offered its stock publicly in 1968 enabling them to expand and open additional parks." (Elsewhere, "After temporarily going public in 1968 a mere four years after its founding, SeaWorld was bought by the Anheuser Busch Companies, Inc. and became its entertainment subsidiary.")
"In 1981, the company [Calgary Power] changed its name to its current name of TransAlta Corporation."
TransCanada - The company was founded in 1951 but I don't know if it was written "TransCanada" from the beginning. I did find https://news.google.com/newspapers?nid=1946&dat=19770728&id=... from 1977 saying "TransCanada", which is good enough to show it was pre-NeXT.
Yes, it is a marketing trend starting almost a century ago (http://pubs.acs.org/doi/abs/10.1021/ie50226a029?journalCode=... shows a 1928 article starting "Thirty tons per day of solid carbon dioxide - that is one measure of the recently complete plan of the DryIce Corporation ..")
However, the MacDonalds, McGregors, and others will disagree on your final statement.
Richard and Maurice McDonald opened the first McDonald's restaurant in 1940.
FitzWilliam, FitzPatrick, FitzGerald, etc. are also proper nouns where more than the first letter is capitalized.
The IJsselmeer written in English preserves the Dutch capitalization rules.
Then there's hyphenated words like "There is no such thing as an ex-Marine ..." (http://www.military.com/marine-corps-birthday/marine-birthda... ), but that leads to the question "what is a word?"
Combined with whyenot's example: "The ex-Marine ate a McIntosh apple at the McDonald's on the IJsselmeer."