What does "polyporus" mean?

Polyporus: A genus of fungi having the under surface full of minute pores; also, any fungus of this genus. Note: Polyporus fomentarius was formerly dried and cut in slices for tinder, called amadou. P. betulinus is common in America, and forms very large thick white semicircular excrescences on birch trees. Several species of Polyporous are considered edible.