出典:Wiktionary
From German Umlaut in the 19th century, from um- or um (“around, re-, trans-”) + Laut (“sound”), from Old High German hlūt. More at umb, loud.
umlaut (複数形 umlauts または umlaute)
umlaut (三人称単数 現在形 umlauts, 現在分詞 umlauting, 過去形および過去分詞形 umlauted)