A Korinthenkacker is someone who is so petty that they are even stingy when it comes to digestive waste products. "Korinthen" are currants and "kacken" is a less-than-medical term meaning something like "to poop." Thus, the "Korinthenkacker" is so paltry that he or she won't leave anything larger than a currant in the toilet. Why that may all seem a bit graphic to you, we're basically talking about a pedantic and small-minded person, who always wants to be right about everything. Think "anal retentive," really.