I suspected the term "umlaut" would trigger some reaction and speculation. As I mentioned I studied German, and
so "umlaut" as the term for that pronuciation mark is the easiest and most identifiable for me (and for many other folks it seems). But is it proper? No. I also studied linguistics in college and there is an internationally accepted phonetic alphabet where each of these punctuation marks has a specific name to prevent confusion. But that was a while ago...and I can never remember those off the top of my head. I guess I should dig out the old text and refresh, it would be helpful on this site. But "umlaut" is just a convenient, lazier way for identifying the mark...but, on the other hand, it works. I don't think if I used the proper terminology people would know what I was talking about. One of the other terms mentioned might be the accurate one, I'm just not sure...back to the books for me!