ruel-bone

Learned borrowing from Middle English rewell bon, ruel bon (“walrus ivory”), from Old French roal, rohal (“walrus ivory”), ultimately from Old Norse hrosshvalr (“walrus”).

ruel-bone (plural ruel-bones)

1. (archaic, literary) A piece of ivory, generally from a marine mammal.
   • 1962, J.R.R. Tolkien, The Sea-Bell:

     White it glimmered, and the sea shimmered
     with star-mirrors in a silver net;
     cliffs of stone pale as ruel-bone
     in the moon-foam were gleaming wet.