"Go ahead, outline "that evolutionary process" for me. I'd sure like to
how you get "fixed focal length" to evolve into "prime." What might the
intermediate steps look like, I wonder?"
Many of the earlier zoom lenses from the 1960's and 1970's comprised an
afocal zooming portion in the front, followed by a fixed focal length
lens group in the rear. That fixed focal length lens group was, and
still is, called a "prime lens". I suspect that this may have led to
all fixed focal length lenses being called prime lenses.
As a side note, this early type of zoom lens automatically had a
constant f/# through zoom. However, it is not nearly as common a
design form as it used to be.
As I've pointed out to you earlier, respected manufacturers such as
Panavision do use the word "prime" to mean fixed focal length. The cat
is clearly out of the bag here, and we might as well get used to
"prime" and "fixed focal length" being synonyms.