Budding rheologists quickly learn about Heraclitus the Obscure. The Society of Rheology has taken one of his quips, "panta rei" "Panta Rei" (Everything flows) and made it the motto of the Society.
While it would be interesting to know what committee was responsible for giving him the description "the Obscure", I've been curious for quite some time what such a description was called. After all, Richard I of England was so blessed ("the Lionheart"), as was James, son Alphaeus ("the Lesser" - now that's a backhanded compliment!), Fredrick II of Prussia ("the Great") and countless others. I've found 2 nearly identical terms to describe the descriptors: epithet and epitheton necessarium. Surprisingly, in modern American English, an epithet usually means a racial epithet. So maybe the Latin option is the way to go. I don't want to be caught "dissing" Heraclitus.