Literally: “currant pooper” / meaning: very pedantic person
The world sees Germans as the only people in the world who iron their underpants. As the only people in the world who will order their clothes by color. As the only people in the world who will call you in panic when they are 5 minutes late for a meeting—and who expect the same from you.
In other words: Germans are said to be quite small-minded people who will break out in sweat if everything is not in perfect order. This is reflected in a plethora of German words for people with this character trait. Erbsenzähler (“pea counter”) is a nice example, but you will also hear Kümmelspalter (“caraway splitter”) or i-Tüpfelreiter (“tittle rider”) pretty frequently. And then, you have the Korinthenkacker as a more extreme version.
You might think of him as a person who does not take an uncontrolled dump but defecates in small, perfectly even-sized portions. I am pretty sure the lady from our local tax office can do that!