Didn’t Flattop introduce Mabuse as another alias a few days ago? (I’m not up enough on Tracy lore to know of Dr. Mabuse is as fictional in their reality as in ours, or if he was a real person a century ago in Tracy’s world.)
(On a PC, windows-period will bring up a special characters menu, the details of which depend on exactly what flavor of Windows you have installed, but umlaut characters should be available.)
“We don’t want to linger on this too long or the fact I’m older than Herr Totentanz might come up.”