Khutu

Khutu was the name given to a material used by medieval Islamic cutlers for knife handles. The ultimate source of the material has been a matter of conjecture for more than a thousand years; Islamic polymath al-Biruni was among the first to investigate it and debate about the material—especially its source—continues to this day. The hypothesized sources for the material have included narwhal, walrus, and mammoth ivory, the frontal bones of bulls, goats, and birds, the teeth of snakes, fish, and hippopotamuses, and the root of a tree. The most recent investigation, by natural historian Chris Lavers, has pointed to the frontal boss of the horns of the muskox.