The Umlaute was one of the very first things I was taught in 57-60 as a military dependent in Germany. The city Nurnburg had an umlaute over the u. I had a German teacher who was German and spoke fluent English. I liked the way he taught language as he would give us twenty words a day to learn. We learned many words and he also taught the proper verbs and prepositions. I had to take another language in the Army and the teacher was not as good.
I also started learning German from a native German in a Department of Defense Dependent school in Germany, took two years of it in college, and spent my junior year in Germany. I also took classes in Russian, a language that seems to have been deliberately designed so as to be impossible for outsiders to master.
The singular is "Umlaut" (masculine, so "der Umlaut"). Plural: die Umlaute (except in the Dative Case, in which case it's: den Umlauten).
Visited Nürnberg last month. In my judgement: A very picturesque town.
The accepted English name is: Nuremberg.
If you liked their Racial Purity Laws, you'll love their sausage (Fränkische Bratwürste a.k.a. Nürnberger). /s
Regards,