In another thread the question was posed:
"Why do we use the word/spelling 'RAW' ?"
I blame Adobe for creating the confusion. In order to prevent any confusion in my own explanations, I began to use the all-caps version, "RAW", to explain files which were camera generated with little or no in-camera processing; pretty much as close to the camera sensor readout as the manufacturer allowed. (Modern RAW files 'do' tend to have some camera internal processing and are not as 'pristine' as many would like.)
But, I digress.
The reason I blame Adobe is because they developed software relatively early in the digital photography revolution. At the time some imaging devices actually read out directly from the imager, and they would stuff the image data out to files directly, with no header or formatting whatsoever. It was just a continuous stream of numbers.
Since there was no organization to the data, you had to know the data length of each imager's readout row, and you had to know how many rows vertically. (There were other things you had to know, but I am simplifying for brevity's sake.)
Commonly, early researchers just called this the "raw" data file, and often the file would have a name and a "raw" suffix. ('flower.raw', for instance.) Early Photoshop was one piece of software which could make sense of these files. (This was waaay before the Adobe Camera Raw module was developed for Photoshop 7.)
For instance, here is a PDF file for an early user manual for Adobe Photoshop 4.0, File Format Specification:
Fell free to download, if you wish.
On page 15, the second section begins for the topic, "Document File Formats".
You should see a line which reads, "If the compression code is 0, the image data is just the raw image data." (I boldfaced the word, "raw" to make it easier to spot here.)
A little further down on the same page, find a table "Table 2–11: Image data" and the second line of the first Description reads, "Raw data = 0, RLE compressed = 1."
In this case the word "raw" has a capitalized "R", just because they are starting a line and using common English text notation. This document was produced in 1997, but Adobe was using the same notation when Photoshop 7 was released in 2002.
However, with version 7.0.1 of Photoshop there was an optional software component: "Camera RAW 1". (Hereafter known as ACR, and yes, that is an acronym.) Please note the spelling of this new product; all-caps.
You see, some camera manufacturers were shipping with a more standardized method of storing camera sensor data, so you no longer needed to know much about the image sensor and raw data file format.
Unfortunately Adobe called these new files "Raw" files, presumably to differentiate between the simpler "raw" data files. But the product which could decode these new files was called "Camera RAW"
So reading those early Adobe descriptions was either comical or confusing, because sometimes you would read a discussion about "raw" data files, but people were erroneously using the "Raw" spelling of the new file format.
Since Adobe had already used the spelling "RAW" in its "Camera RAW" product, I decided that also using the all-caps spelling to describe the file types would help to differentiate these new file types from the old.
I searched all over to find a definitive image for the optional ACR plugin packaging for Adobe Photoshop 7.0.1, but the best I could find was the Photoshop wiki page text, last updated July 2018, ...
... and they describe the "Camera RAW 1.x (optional plugin)"
But later Adobe did incorporate ACR into Photoshop CS and all the Adobe documentation describes the files as "Raw" type, but by then the damage had been done.
Anyway, ACR 1 was when Adobe used the RAW spelling notation (briefly), so I blame then for the earliest use.