"wool coat of a sheep," Old English fleos, flies "fleece, wool, fur, sealskin," from West Germanic *flusaz (source also of Middle Dutch vluus, Dutch vlies, Middle High German vlius, German Vlies), which is of uncertain origin; probably from PIE *pleus- "to pluck," also "a feather, fleece" (source also of Latin pluma "feather, down," Lithuanian plunksna "feather").