Always learning new stuff on these threads. I looked up "diæresis" and found that it's not the same thing as an umlaut. I knew it was used differently, but didn't realize it had a different name. Thanks
One of the useful accents that disappeared from written English with the introduction of the typewriter.
Computers means it can come back - But nowadays not as easily as on my old WP Program Protext, where typing ALT-" after a vowel would put a diæresis/umlaut over the vowel - Other ALT combinations gave other accents (I miss Protext)