O with diaeresis

Swedish, Finnish, Icelandic, Hungarian and Estonian treat ö as a letter in its own right, and German uses it as an umlaut. Danish and Norwegian write the same sound as ø.

Rock music gave it a second life. Blue Öyster Cult added an unnecessary umlaut to its name, most likely in 1971, apparently the first hard rock band to do so; the critic Richard Meltzer said he suggested it, and Motörhead later did the same.