Anyone wondering about Schiermonnikoog could have googled themselves here ofcourse:
http://en.wikipedia.org/wiki/Schiermonnikoog , which says it a lot better than I could have. It's a tiny island off the coast of Frisia.
Grey Monk's Island is a fair translation though there is some debate about the skier (or schier in Dutch) actually referring to a color. Skier -does- translate to gray, but a more common way to refer to the color would have been griis or grijs.
Since it's not called Griismuntseach or Grijsmonnikoog, it might be good to think about the other (currently more common) uses of the word skier / schier in Frisian and Dutch. It also means either 'protruding piece of land that is only attached to the mainland on a single side' (i.e. peninsula) or 'type of landscape where erosion has removed all or most of the relief'. But the net doesn't have enough resources to see if that makes any sense, since I'm unable to find sufficiently old maps, if any exist at all.
This one is nice though:
http://watwaswaar.nl/#dE-yu-4-1-1v-1-46lc-4DGC---hOr
Ofcourse, none of it has anything to do with the oversized grand piano's on the beach...
Greetings,
Grismar.