>Eierschalensollbruchstellenverursacher

That's not actually what they're called, it's an overly descriptive contrived way to get a long word, like "Donaudampfschiffahrtsgesellschaftskapitän". Imagine someone in english saying "Ink-to-paper-writing-implement" instead of "pen".

You'd call it an "Eieröffner"(Egg opener) or "Eierköpfer"(Egg beheader).