Originally Posted by
DanK
That said, this is a weird case. ISO calls this a name, but it clearly came from the acronym. And if it's a name, this makes it an outlier. Of the top of my head, I can't think of other trademarked names that aren't acronyms but are written in all caps anyway. I wouldn't be surprised if there are some, but I can't think of any.
I'm going to find it very hard to get in the habit of saying eye-so rather than I S O, both because of many years of habit and because in my circles, it's often the not terribly well informed photographers who have been saying eye-so.