Randomly from Wiki, an entry on the "heavy metal umlaut":
The heavy metal umlaut, or "rock dots", is an umlaut over letters in the name of a heavy metal band, such as Mötley Crüe or Motörhead. The use of umlauts and other diacritics with a blackletter style typeface is a form of foreign branding intended to give a band's logo a Teutonic quality. It is a form of marketing that evokes stereotypes of boldness and strength commonly attributed to peoples such as the Vikings; author Reebee Garofalo has attributed its use to a desire for a "Gothic horror" feel. The heavy metal umlaut is never referred to by the term diaeresis in this usage, nor is it generally intended to affect the pronunciation of the band's name.