When Tony Thorne first started researching slang, he was largely on his own. This was in the ’80s, when, according to Thorne, the academic community “virtually ignored” slang as a part of linguistics.

Several youth words include "Das crazy" are displayed on stage on a screen during the German Youth Word of the Year ceremony at the 77th Frankfurter Book Fair. Hannes P. Albert/dpa The phrase "das ...